135 418 THS mr‘mE-{e A 7. 4 UBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE moo Wm.“ A DISTRIBUTIONAL STUDY OF THE GENUS PUTAMOGETON IN MICHIGAN, INCLUDING SOME ECOLOGICAL NOTES ON OTHER AQUATIC GENEKA Thesis submitted to the faculty of Michigan State College in partial fulfillment of the requirements for the M.S. degree Henry Qggting 1927 IHESIS ACKNOWLEDGEMENTS I wish hereby to express my appreciation for the guidance and. assistance given me by Dr. H. T. Darlington {throughout this work and. for the advice and interest of Dr. E. A. Bessey. 1. $5393 A‘Distributional Study of the Genus Potamogeton in Hichigan, Including Some Ecologica1.Notes on Other Aquatic Genera Intro duct ion (The genus Potamogeton forms one of the important elements of aquatic vegetationf‘ no publication Which concerns aquatics in.general is complete without a discussion of the relation- ships of the genus with the other plants of aquatic habitat. {All contributions to the vegetational conditions in marginal waters must recognize its importance because the genus con- stitutes a vegetational unit which.makes up a large part of the inland aquatic vegetation) The‘United States Department of Agriculture has done con- siderable investigation concerning its value as a game food. (The starchy tubers and tuberous rootstocks are the favorite food of most ducks and the seeds and buds are eaten when available. The filiform types such as P. pectinatus are often eaten in their entiretyfi methods of propagation and the con. ditions of growth are being studied so that the game preserves may be planted. (In its relationship to animals, the genus is as important as any aquatic group. unskrats eat the plant tubers, while the larger fish feed on the tenderer forms. For every species of Potamogeton there are several species of insects whose larvae feed.upon the plant or at least pass a period of their 2 lives upon.it.i These in.turn may be related to the fish which feed upon.them. Davis says, "plants furnish places of nesting, of refuge and of rest for fish, and a study of Walnut Lake records shows that the abundance of many fish and their permanence at any station was largely correlated with plant growth (1'7I'."‘ It is evident that the relationships of aquatic plants to animals will bear considerable investigatiml and that results may be of economic importance. I {.As marl-forming agents, the various species of Potamogeton probably stand next to the Characeae in importanceJ In the great peat deposits of the state, bordngs invariably show the presence of some Potamcgeton in the lakes of the past and in sufficient abundance to aid materially in the filling of the lakes and the building up of much lands. Considering the importance of the genus, it would seem that a survey of its distribution in.a state so rich in con- ditions favoring its growth would be entirely Justifiable. To determine the distribution, the herbaria of the Michigan State College, the University of Michigan and the Field Columbian museum of Chicago were studied, as well as the private collections of Cecil Billington.of letroit, C. W. Fallaes of‘Petoskey, and Professor B. A. Walpole of East Lansing. In addition, the writer made extensive collections in several counties in western.M1chigan. All available publications *Numbers in parentheses refer to bibliography. were consulted to increase the distribution records, but be- cause of the critical nature of the genus, only the reports which seemed most reliable and those of the commonest species were recorded. (Agnes Arber in her book on aquatic plants says "The Pondweeds are an exceedingly difficult group from the view point of the student of systematic botany, as the numerous species can, in many cases, only be discriminated as the re- sult of much experience\(2)'. This difficulty of identification is due principally to the extreme variation of species, with the result that few Specimens can be identified without care- ful investigation. Because of the critical nature of the genus, experienced students of aquatics have divided the group into hundreds of sub-species and varieties. This is particularly true of such authorities as Fryer, Bennett, and Blgstrom who have made the study of aquatics a life work. To consider even a part of their fine disoriminations of species and sub-species would require far more study and investigation than this survey involves. The nomenclature as found in Britten and Brown’s I'Illustrated Flora of the Northern States and Canada*, 2nd edition, has been.used.throughout this work. For identifying the more difficult forms it was necessary to supplement the Britton.and Brown key with several others and of these the key in Gray's"flew manual of Botany? 7th edition, and the key of Thomas Mbrong as found in his ”Raiadaceae of North America" 4 were of most assistance. (Any further reference to Britton and Brown or to Gray's manual applies to the above editions). Environmental Relations {The aquatic habitat is so uniform and requires such definite characteristics_for’growth that the vegetation tends to be uniform in character:‘ The submerged portions of all aquatics show tendencies toward simplification both in tissue structure and general form. The genus Potamogeton is no ex- ception. Conducting tissues show no complexity, and other differentiation is reduced to a minimum. Mbst of the submerged leaves are but three cells in thickness. The two outer layers form the epidermis and the single layer between makes up the mesophyll. The epidermal cells are thin-walled, non-cutinized and often contain.more chlorOphyll than the mesOphyll cells. This gives the leaves their characteristic deep green coloration. Further tendency toward simplicity can be seen in the form of the submerged leaves. All but a few are elongate, linear or ribbon-like and sessile on the stem. Species such as P.americanus and P. perfoliatus have leaves which are somewhat elongated and taper to short petioles. This simplicity and uniformity makes identification difficult but to make matters worse, in the genus Potamogeton, the problem of variability in leaf form must also be contended with. The fruits develop characteristically for each species. Two species may often be distinguished by good mature fruits only. The leaf venation, the type of stipule and manner of its attachment, may usually be considered as invariable, and these aid materially in identification. An illustration of the forms difficult to identify is the amphibious type of floating-leaved species. These are dwarfed, coarse forms, usually lacking submerged leaves and often without fruits. They develop when the water drys up or recedes to lower levels, leaving the aquatic plant to die or adapt itself to the new conditions. Mbst water plants, unless highly specialized for aquatic life, are capable of producing such land forms when left in this condition. It is probable that the types having floating or aerial leaves are most successful be- cause the least change is necessary for their establishment. In the genus Potamogeton the types with coriaceous, floating leaves are most eimmonly found in this condition. Fortunately, the leathery, floating leaves and the stipules retain their ' normal characteristics and they aid in identification. Occasion- ally fruits are produced, which simplifies matters somewhat, while comparison with forms in.ad3acent water may also aid. Perms collected.which were growing in the amphibious or land condition are P. natans, P. americanus and P. heterqphyllus. In this.condition these lack their submerged leaves. The float- ing leaves are shorter and heavier than in.the water forms and some were collected which were partially buried in the mud. Although the general form of a given species may be ex. \tremely'vatiable, there are certain characteristics which are 6 e constant. The floating leaves are insariably coriaceous and unwettable, due to a peculiar, wax-like coating not present cn.submemged parts. unlike terrestrial plants, these leaves can not yield when.battered by heavy rains, nor can.they escape the constant motion of the water on which they float. is a consequence these protective features are necessary to permit them to hold their positions successfully. In some submerged formo, the entire plant is flexible and moves as a whale with the fluctuating water. This is more true of the filiform and ribbon types which are often two or three times as long as the depth of the water in which they grow. PotamOgeton natans has the stem-axis fixed in the ground at an angle and by one end only. From this the petioles arise at an angle from pliable points of attachment which permit the leaf to respond to every water movement without resistance. (Light passing through water is reflected at the surface, absorbed by the water, and retained by substances in solution and suspension to such an extent that all submerged aquatics are of the “shade plant" typeI) They invariabhg have delicate leaves, little palisade tissue, and contain.chlor0phyll in the epidermis. (It is possible that the filamentous, linear forms are produced to increase the leaf surface for combating the diminished light in.water. fit is known.that darkness will cause elongation in some terrestrial plants (57). 'The writer is of the opinion that this effect may a: observed in some species of Potamogeton.and that it may account for the variation in length of leaf in some casess) Potamogeton.epihyggu§, collected in Pigeon Lake, Ottawa County, has excessively long, submerged leaves. Other species found here in the deeper water have noticeably elongated submerged leaves. The water coming in is slow moving and drains from a boggy area.which gives it a dark brown color. In Black Lake the water also has a dark color due to factory waste. Here the linear-leaved Species, eSpecially when growing in water of any depth with the resultant diminished light, tend to grow long and to float upon the surface, while the lower submerged part of the plant often reduces to the main stem only; Potamogeton compressus in particular was observed in this condition. {Another factor which may produce elongation in aquatic plants is strain due to current. This was brought to my attention again and again in the field) Whenever a Species of Potamogeton was found growing in a swiftly moving stream, it was elongated far beyond the depth of the water in which it grew. Experiment has proved that a plant subjected to a steady pull in the direction of growth will eventually grow longer than one not so treated (37). It seems reasonable to conclude that the ex- treme elongation of these specimens was due, at least in part, to the pull exerted by the stream flows In connection with stream.flow, rheotropism.should be mentioned. Arbor says that plants growing in water which flows in.a definite direction tend to grow in the direction of the .current, regardless of the strength of that current. All specimens of’Potamogeton collected in streams illustrated this phenomenon conspicuously. The factors influencing variation in leaf form are probably many. The problem has been studied from various angles by several botanists and the conclusions are still quite general. /The concentration of the medium combined with nutrition probably forms an important factor. Transpiration has also been suggested as having some effect, as well as the type and fertility of the substratumfi(15). Life Habits {The genus is so variable and adapts itself so easily to changing conditions that some species may be found in almost any body of water in.M1chigan. Stagnant or extremely filthy water, however, is not conducive to Potamogeton growth)) Where the water is fresh and not too exposed or swift flowing, at depths varying from two decimaters to eight meters, some forms may almost invariably be found. Beyond this depth or in more ‘Open.water it is almost impossible for the larger aquatics to establish or maintain.themselves, with the results that the aquatic vegetation is someWhat concentrated along the margins of the water. Competition and the varying needs of the different types of vegetation have resulted in a definite arrangement of groups with relation to each other. These zones are almost invariable and are an outstanding characteristic of aquatic vegetation. But a comparatively few species can tolerate aquatic conditions and as these conditions are quite uniform everyihere, aquatic floras are everywhere very similar. The few types adapted to aquatic life can endure certain conditions and no others, so that they are always feund in definite habitats, always in the same zones, each zone dominated by a Species or a group of species. The relationships are ordinarily Just as might be expected. .Ihere there are large floating leaves, submerged types could hardly be expected to grow in the shaded waters beneath. These submerged forms usually form a zone by themselves. The semi- aquatics are found in.shallow water near the shore.) {The attached marginal vegetation may ordinarily be divided into four general zones.§ As conditions bearing on vegetation may vary, these zones must be modified for almost every lake when details are considered. (First, along the Shore in shallow water and to a depth of a meter, is a zone characterized by sedges and rushes.e Along the outer margin of this zone a few of the larger leaved Species of Potamogeton may be found, es- pecially those with floating leaves.) or these :9. natans 13 a common form. ‘The second zone is made up almost entirely of plants with floating leaves such as Nymphaea, Nelumbo and Castalia. Because of their habit of covering the entire water surface with their large leaves, the submerged aquatics are forced to live outside the floating-leaved zone. In the deepest waters of the lake, vegetation is extremely Spares and is limited almost entirely to species of M and __Cha_r;a_. Between this deep-water zone and the floating-leaved zone, we find the genus 10 Potamogeton thriving as the dominant planth Here, almost any or all of the Species may be found. When the water lilies or large floating-leaved types are absent, Potamogeton may occupy all the area from deep water to the sedges. (The width of the zones varies with the slepe of the bottom. A steep narrow shelf with a sudden drOp to deep water, limits the width of the zones and the number of Species which may take root there. Under such conditions the Potamogeton zone may not be present at all or only a few scattered forms may be found along the margin of the drop off. This condition is found in small deep lakes which are gradually disappearing. Then again, one part of a shore line may be in this steep con- dition while another in the same lake may have a wide shallow margin, gradually increasing in depth. The distribution of the genus here is obvious. Associated with the genus PotamOgeton are several other genera whose conditions for growth are practically the same. Elodea, Vallisneria, and.yyZiOEhyllum Species are common while Brasenia is often found scattered through the two central zones. Their demands seem similar to those of the floating-leaved Potamogeton such as P. natans. Unattached species of_§e§§tg- phyllum and Utricularia are common also in almost any zone, and the small duckweeds such 33.22522 and WOlffia may be found any. where, although concentrated mostlyin sheltered waters. The genus Potamogeton is not limited to lake margins alone. In some shallow water bodies they may be scattered throughout. ll HeweVSr,.if these be lakes of any size and unsheltered, per- mitting rough water, then floating-leaved types in particular are rare, and the open water will have fBW'if any Species. Potamogeton compressus, which is heavily veined and has linear leaves and stem, combines strength with a minimum resistance to wave action. Specimens were collected in the center of Black Lake, Ottawa county, where they were exposed to the most extreme weather conditions. more fragile types such as g; ppusillus, probably would not survive in such locations, although having the same general form. Collections of almost all Species were also made in streams of widely varying character. wThe biological wealth of a stream varies inversely with its rate of flow, according to Pond (44). This statement is applicable to the genus Potamogeton; for when- ever anything checks the flow of water, there conditions are more favorable for its develoPment. Where the flow of the stream is checked, there is an accumulation of organic material and a deposition of rich alluvium, with the consequent increase 01 soil fertility and an increase in vegetation. Some observations of habitat made in Black River, Ottawa county, are of interest. Almost without exception, the smaller filiform.Species were found in shallow water with sandy or gravelly bottom, while P. americanus was invariably found on clay bottom or hurt a clay bank. Species with linear or ribbon- like leaves seem.best able to survive in shallow and swift moving streams. Several of these species were collected from 12 shallow, swift-flowing, sandytbottomed streams at scattered stations. The water often was little more than a decimeter in depth while the plants were often a meter or more long and floating out on the surface. The gelatinous or slimy Sheath characteristic of so many water plants is conspicuously present in this genus. In some cases it is only about the seeds and in others the young leaves and growing points may be encased in it. Again, the entire plant may have a thin coating. It has been suggested (44) that this covering may protect amphibious forms and others too, from too rapid loss of water when exposed. Perhaps it is a pro- tection for young buds and shoots against devouring animals. In submerged plants (2), the mucilage hinders the entry of water. Its true function has seemingly not been determined. An incrustation is often found on the submerged leaves and stems of many of the Potamogeton species. This in- crustation is a dpposition of calcium carbonate. Several theories as to the reasons for its presence have been advanced but nothing very definite has as yet been determined (53). The commonest theory states that when the plants withdraw carbon dioxide from.the water for food manufacture, the soluble bicarbonate of lime which is present in the water, is reduced to the insoluble neutral carbonate and deposited.upon the Plant surface. 0231150035 _. 0300.5 + co, + 1120 Another theory considers the oxygen liberated by the plant as a 13 catalytic agent which acts on the bicarbonate to change it to a.neutral'carbonate. The most recent explanation rests upon the discovery that's soluble calcium salt of succinic acid is present in.the cell sap of QE§£§° "The occurrence of this salt in the sap of other plants has not been determined, but as succinic acid is a very probable by-product in the ordinary processes of plant physiology, its wide distribution may reasonably be expected. As the calcium salt escapes from 92335 by osmosis it is most likely decomposed with the formation of the insoluble carbonate.I (44). .A considerable amount of careful work has been done on marl of late and investigation shows that, although the pre- cipitation of calcium carbonate by plants is only one factor in the production of marl beds, still it is a factor which is great enough to be economically important. On some species of Potamogeton, the incrustation is almost invariably present while on others it is sometimes present. On the ribbon-leaved Species of Potamogeton and such aquatics as vallisneria, it seldom lodges, for their movements with the water probably set it free as soon as it is produced. In all cases the incrustation may easily be removed from the leaf. Its presence or absence does not seem to affect the life pro- cesses of the plant, as the most heavily incrusted Specimens may be as large as those without a trace. So far as is known, the incrustation is a result of processes taking place within the plant and has no particular effect on the life processes 0 14 of the plant which precipitates it. “The genus Potamogeton includes in its vegetative re- production every possibility or means employed by other aquatics. Some species prOpagate by vegetative fragments. Some have rhizomes and tuberous rootstocks to carry them through the ‘winter. Still others produce vegetative winter buds - hiber— nacula, propagules or turions as they are variously called. These break off, drOp to the bottom and start new plants in the Spring. Although vegetative reproduction is possible in so many ways, sexual reproduction is also well develOped. Wind is usually the pollen distributor and the Spikes will be found protruding Just above the water. In P. praelongus, the stem shortens after pollination and the Spike is drawn under water where the seeds mature. Several of the completely submerged Species are pollinated under water. In these, the pollen grains are filamentous structures that are as heavy or heavier than water _and lack the thick exine characteristic of aerial pollen (15). Such pollen grains upon release float Just beneath the surface and may come into contact with the long exserted stigmas. Some members of the genus have almost completely ceased to produce seeds. PotamOgeton robbinsii Oakes is the rarest of North American Species to fruit with the exception of Pi interruptusixitaibel which bears floral Spikes quite freely, but is not known to mature fruit in this country, though it does in Europe (28). Dr. Thomas'Morong writes as follows in regard to the‘fruiting of P. robbinsii: "Very rately,in years when 15 the waters are low, the flowering spikes rise above the surface and perfect a few fruits. Dr. Robbins saw but one fruit, collected in Oregon by Hall. .Mr. Faxon collected a fdw fruit- ing Specimens in Jamaica Pond, massachusetts, in 1880. Besides these, I have never known another instance, although the plant is very prolific in the localities where it occurs." Of the specimens of P. robbinsii I examined, none bore fruits. Specimens collected and observed in the field had Spikes in various stages of maturity, and although a few appeared to have had fruits, none were collected or seen. I}; interruptus was not collected, but of the specimens examined, None bore even a trace of a spike. Emmekine Mbore says of P. robbinsii that in spite of the absence of fruits, pro- pagation is readily affected. The branches, especially those with short internodes, become thickened and hardened through the storage of starch and when detached, function as propagative structures. As this enlargement and induration may take place at various points along the main axis, the final dismemberment of the whole plant provides enormous possibilities for the V multiplication of the Species. ' P. pectinatus and P. filiformis are propagated by small tubers. These form at the ends of runner-like stems which spread in all directions from the main axis of the growing plant. P.Aperfoliatus and P. americanus grow in beds er small groups. All are connected by a network of underground runners or roots. .Miss lbnre explains these as non-tuberous underground l6 stems, rooting at the nodes and carrying the plant through the winter by the enlarged terminal portions which bear scaly buds. P. heterophyllus has its individuals connected in a series by an underground portion which is a series of short nodes and swollen internodes and Miss Mbore calls this "pro- pagation by tuberous rootstOCks". This underground system of migration.is very rapid in.water plants, the soft mud of lake bottoms offering but little resistance to growth. Cowles says that a meter advance in a year is not uncommon. It is quite generally agreed that temperature variation in water is considerably less, taken the year around, than on land. In spite of this, there is always a possibility of freezing. To overcome this possibility, Species which grow the year around, like P3 crispus, Sink to the bottom in winter. Others withstand the most extreme cold by means of their seeds or winter buds. These winter buds are formed by the tips of branches with a closely packed, overlapping mass of leaves and stipules. These form in the late summer, and in the faLl they separate from the parent. Due to their compactness, they are heavier than water and so Sink to the bottom where they rest through .the winter. In the spring they resume growth like a simple vegetative branch. P. compressus produces conSpicuous winter buds and also plentiful fruits. P. friesii and P.ppusillus, which are smaller forms, also commonly produce both buds and fruits. Miss Arbor 17 has shown that bud formation, in these types particularly, can be directly connected with unfavorable growth conditions. To bear this out, I found that the smallest and weakest plants usually bore the most and the largest winter buds. These Species bearing both buds and fruits have a general distribution and are very common forms. _It is probable that this double method of reproduction helps to explain this distribution. P. crispus forms a Slightly different type of bud. Miss Incore calls it a bur. Mbrong groups both types together and speaks of them as propagating buds while Miss Arber calls them all turions. The P. crispus bud is merely a much shortened branch with reduced leaves and a concentration of starch within it. The entire bundle hardens and this hardness combined with the serrulate margins of the leaflets gives the feeling and appearance of a bur. Large numbers of these buds are formed and as nearly as I can learn, fruiting in P. crispus is quite uncommon. No fruits were found at the three stations where it was collected. The advantage in carrying the plant through the winter by means of these buds is obvious. However, vegetative reproduction of this type has its disadvantages, chief of which is the limitation in rate of diapersal. The establishment of such species in distant habitats is almost impossible unless there are continsus waterways between and the result is a slow migration. 18 - Distribution. Before attempting to draw any conclusions from the records of distribution, several factors should be considered which influence these records and which will modify the interpretation somewhat. Potamogeton Species are often found in almost inaccessible places. USually they are covered with a slimy Sheath which makes them difficult to handle and requires special pains in preserving Specimens. After collecting, they decompose very quickly. Specimens in fruit are necessary for the identification of some Species and fruiting specimens are often lacking. With these disadvantages it is obvious why collections of aquatic plants are limited. Records‘for some Species are very limited. most of these bear close resemblance to more common Species and can only be distinguished by careful study. The result is that the average collector does not recognize them in the field or after collection. In this class are P. oakeSianus Robbins which is scarcely distinguishable from P. natans L. except in mature fruiting condition. Enough Specimens of P. oakeSianus were ex- amined and collected to feel certain that it grows in the state and the wide separation’of the points of collection would indicate that further search may reveal a general distribution. Several of the filiform Species are even more difficult to recognize and identify. Because of the variable character of the genus, the several 19 species.are capable of adapting themselves to almost any condition.of habitat with the result that most of the forms have a general distribution throughout the entire state. This is particularly true of the more prolific forms such as P._perfoliatus; P. hetergphyllus, P. americanus and the type Species P. natans. There is one exception to this general distribution. An area including Otsego,Montmorency, Kalkaska, Crawford, WSxford and Missaukee counties has no record of any specimens whatsoever. This would seem to indicate that conditions here are unfavorable to the growth of the genus. However, a study of detailed county maps of this area Shows that all have at least enough ‘water to supply the conditions necessary for the growth of Potamogeton. Adjoining counties on all sides show general distribution for most species. The fact that the blank area is the same for every Species leads to the conclusion that the area has probably not been sufficiently botanized. Previous to the summer of 1926 the counties of Newaygo, Ottawa and Barry showed practically no records of PotamOgeton collections. During that summer the writer botanized in these three counties with the result that practically all species found in the state were found there also. I conclude therefore, i that the total absence of records in some regions, is due not to the absence of Potamogoyon but to the absence of botanists. Considering the species more in detail, we find several exceptionsrto the general conclusions. Several species have 20 not been collected or reported in the state. Others are so rare that the authenticity of reports may be doubted, es- pecially Where there is a close resemblance to some more common form. The greatest possible care was used in the identification of such forms. They were only recorded when the Specimen had been thoroughly checked. Reports were not recorded at all in cases where there was room for doubt. Of P. faxoni Morong. but two reputed Specimens were ex. amined.- The one from Genesee County collected by D. Clark agrees entirely with descriptions obtainable. Hewever, the specimen ' of S. H. Camp, from Jackson County is immature and also has many of the characteristics of P. americanus 99‘ §._ Gray's manual holds that P. faxoni Mbrong. is an infertile hybrid of .P' alpinus Balbis and P. americanus C.& S. If this is true, mid neither of these Specimens had mature fruits, then the poor distribution is somewhat explained. Its close resemblance to these other forms may also explain the lack of specimens on record for the state. . In Britton and Brown's Illustrated Flora, P. varians‘Mbrong is spoken of as a hybrid of P. angustifolius Berch. &‘Presl. and P. heterOphyllus Schreb. and it is limited to Mystic Pond, Redford, massachusetts. Five good Specimens were examined which were originally collected and identified by reliable botanists. The Specimens were collected in widely scattered stations in the state and the evidence would seem to indicate its establish- ment in,Mlchigan. The records may be limited because of its 21 close resemblance to P. heterophyllus Schreb. P. crispus L. is a European Species which has become es- tablished in the Atlantic coastal states and is gradually migrating inland. One specimen was examined which had been collected by Pennington in van Buren county and during the summer, the writer found P. crispus growing prolifically at three distinct stations in Ottawa county. The manuals limit the range of P. criSpus to the eastern states. In 1913, E. D. Bull wrote a short article on the advance of the species and showed it had but recently established itself in Illinois and Indiana and that the points of establishment were along connected bodies of water. Because of its means of diSpersal, previously mentioned, this seems entirely within reason. These water bodies mentioned by Hull are connected with Lake Michigan and so migration to other nearby water bodies connected with it could ‘well be expected. The collections made in.M10higan were in the southwestern part of the state, in small lakes connected with Lake Michigan and it seems reasonably possible that the species could have migrated to these points from Illinois and Indiana where it was already established in 1913. I have found no other record of its growth in the state, and in the several counties I worked I found no evidence of its presence. Of the thirty five Species as listed in the Illustrated Flora of Britton and Brown, seven have not been found in the state. P. pulcher Tucker-:seems to be limited almost entirely to the Atlantic coastal states and the south. P. gysticus 22 Morong, a depauperate form of P. perfoliatus I... is a local species found in a few stations in Massachusetts. P. confervoides Reichb., a delicate, filiform Species, is restricted more to cold streams or mountain ponds and is common in the New England states, particularly Maine and New Hampshire. It is possible that further investigation may show its presence in the Upper Peninsula of Michigan. P. gemiparus Morong is a local Species found in the Atlantic states only. The range as given in Gray's Manual and the Illustrated Flora of Britton and Brown for P. diversifolius Raf. and P. dimorphus Raf. includes Michigan but no Specimens were collected or located for examination. Key to the Species of the genus Potamogeton in.Michigan. la. Plants with both floating and submerged leaves. 2a. Submerged leaves bladeless, reduced to phyllodes. 5a. Nutlets pitted, 4-6 mm. long, 3 mm. wide -- l. P. natans. 3b. Nutlets not pitted, 3 mm. long, 2 mm. wide -------- 2. P. oakesianus. 2b. Submerged leaves with a proper blade. 4a. Submerged leaves capillary to linear. 5a. Submerged leaves capillary to linear-setaceous, 0.1-0.5 mm. wide, l-nerved - 22. P. vaseyi. 5b. Submerged leaves linear, broader than 5a, I several-nerved. 6a. Leaves ribbon-like, obtusely pointed, coarsely cellular-reticulated each side of midrib -- T4. P. epihydrus. 6b. Leaves broader at base, acute; no cellular-reticulation --- 8. P. heterophyllus. 4b. Submerged leaves lanceolate to ovate. 7a. Submerged leaves not of same type at upper and lower part of stem. 8a. Upper submerged leaves oval or elliptic, lower lanceolate, not pellucid; plant grenn ------------------- 5. P. amplifolius. 8b. Upper submerged leaves petioled, lowest sessile; semi-pellucid; plant 24 reddish-tinged throughout ---— 5. P. alpinus. 7b. Submerged leaves all of same type. 9a. Submerged leaves petioled. 10a. Floating leaves elliptic. lla. Floating leaves broadly elliptic, rounded or subcordate at base -- 10. P. illinoensis. 125. Floating leaves narrowly elliptic, tapering at base -— 6. P. americanus. lOb. Floating leaves obovate or oblanceolate, tapering at base ---—.7. P. faxoni. 9b. Submerged leaves sessile or subsessile. 12a. Fruit only 2 mm. long, obscurely S-keeled ------------ 9. P. varians. 12b. Fruit 3 mm. long, distinctly 3- keeled ----------- 11. P. angustifolius. lb. Plants with submerged leaves only. 15a. Stipules free from petioles. l4a. Leaf-blades rather broad, 6 mm. to 4 cm. wide, lanceolate or oblanceolate to ovate, several- to many-nerved. 15a. Leaves sessile or short-petioled, not claSping. 16a. Fruit S-keeled, 2.5-4 mm. long; Spikes 2.5-5 cm. long --------- 11. P. angustifolius. 16b. Fruit scarcely keeled, 3 mm. long; spikes 5-7.5 cm. long ......... 12. P. lucens. 25 15b. Leaves claSping or half-claSping. 17a. Leaves half-clasping, elongate with rounded cucullate tips; stipules conSpicuous; fruit sharply keeled --------------- 13. P. praelongus. 17b. Leaves cordate-clasping, if elongate the tips plane tapering; stipules inconspicuous or soon reduced to shreds; fruit rounded or scarcely keeled -------------- 14. P. perfoliatus. 14b. Leaf-blades narrower than 6 mm.(except P. criSpus), linear to oblong-linear; 1-7 nerved. 18a. Leaves glandless at base. 19a. Leaves linear, 3-5 nerved (except 16); 1-6 mm. wide. 20a. Leaves delicate, 1-2 mm. wide, obscurely 3-5 nerved -------------- 18. P. foliosus. 20b. Leaves coarser, 2-6 mm. wide, two ranked. 21a. Leaves 5-nerved, caarsely cellular-reticulate -along midrib, ribbon-like -4. P. epihydrus. 21b. Leaves with 3 principal and many fine nerves -- 16. P. compressus. 19b. Leaves variable in shape, linear, oblong-linear, or linear-lanceolate, 3-7 nerved, 2-16 mm. wide. 22a. Leaves crisped, oblong-linear, serrulate, 3-7 nerved ---------- 15. P. criSpus. 22b. Leaves not crisped, entire, pellucid, upper 26 often petioled, lower sessile. 23a. Entire plant suffused with red; leaves obtuse, or rarely acute, narrowed at base; fruit 3-keeled, middle keil sharp -5. P. alpinus. 23b. Plant green, leaves acuminate or cuspidate; fruit indistinctly 3-keeled - 8. P. heterOphyllus. 18b. Leaves 2-glandular at base. 24a. Leaves 3-nerved; Spikes capitate. 25a. Leaves acute, cuspidate, l-l.5 mm. wide; fruit 5 mm. long ----------- 17. P. hillii. 25b. Leaves obtuse, mucronate, 1 mm. wide; fruit 2 mm. long ----------------- 23. P. pusillus. 24b. Leaves 3-7 nerved, Spikes notcapitate. 26a. Leaves strict and revolute, 3-5-nerved, acuminate ------------------ 21. P. rutilus. 26b. Leaves not as above, 3-7 nerved, obtuse, mucronate or cuSpidate. 27a. Spikes ovoid, 6-9 mm. long; peduncles slender, erect ----------- 19. P. obtusifolius. 27b. Spikes interrupted, 7-12 mm. long, peduncles thicker than stem, sometimes thickening upward -------- 20. P. friesii. 13b. Stipules adnate to leaves or petioles. 28a. Leaves very narrowly linear, less than 2 mm. wide, capillary to setaceous, l-nerved or nerveless. 27 29a. Free part of stipule shorter than sheath; stigma broad and sessile. 30a. Sheath of stipule less than 8 mm. long ------------------ 24. P. filiformis. 30b. Sheath of stipule more than 14 mm. long ----------------- 25. P. interior. 29b. Free part of stipule equal to sheath; stigma capitate; style apparent - 26. P. pectinatus. 28b. Leaves linear, 2-6 mm. wide, nerves 3 to many. 31a. Leaves entire, 3-5 nerved ------- 27. P. interruptus. 31b. Leaves minutely serrulate, finely many-nerved -------------------- 28. P. robhnnsii. 28 l. POTAMOGETON NATANS L. (floating). 2. Very common. Distribution general thruout. Ponds and slow moving streams, depths varying from 1/2 - 2 meters. Often found in exposed water. This is the type Species of the genus and is large and conspicuous. Submerged leaves reduced to phyllodes. Heavy, brownish-tinged, floating leaves attached at right angles to petioles. Fruiting July and August. Specimens examined: Berrien Co. (H.T. Darlington, 1917); Lenawee Co. (0. Billington, 1914); Monroe Co. (B.F. Chandler,l9l3); Van Buren Co. (H.S. Pepoon,l904); KalamazOO Co. (E.B. mains,1913); Jackson Co. (S.H. a D.R. Camp, 1897); Washtenaw Co. (J. Dawson); Wayne Co. (C. Billington, 1915); Barry Co. (H. Oosting,1926); Ingham Co. (C.F. Wheeler,l900); Livingston Co. (F.L. Stearns,l920); Oakland Co. (B.A. Walpole,l9l9); Macomb Co. (Cooley,l840); Ottawa Co. (H. Oosting,1926); Mbntcalm Co. (C.F. Wheeler,l900); Kent 00. (A.J. Pieters,1897); St. Clair Co. (C.K. Dodge, 1904); Mhskegon Co. (C.D. McLouth,l899); Heway 0 Co. (H. Oosting,1926); Emmet Co. (c.w. Fallas,1897 ; Iosco Co. (H.T. Darlington,l918); Oscoda Co. (H.T. Darlington,l9181; Cheboygan Co. (F.C. Gatesfl9ll); Gogebic Co. (E.A. Bessey, 1920); Marquette Co. (A. Dachnowski, 1906). Reported from: Cass Co. (H.S. Pepoon,l907); Calhoun Co. (C.F. Barr,1908); Allegan Co. (F.A. Loew,l9l3); Lapeer Co. (W.A. Brotherton,l921); Tuscola Co. (C.K. Dodge,1921); Huron Co. (C.A. Davis); Bay to Cheboygan Co. (Occassional C.K. Dodge,1921)° Chippewa Co. (C.K. Dodge,1921); Schoolcraft Co. C.K. Dodge,1921). POTAMDGETON CAKESIANUS Robbins. (named for Cakes). Infrequent. Distribution probably general. Habitat same as P. natans which it closely resembles except in size. Seeds desirable for identification. Fruiting July, August. 3. 4. 29 Specimens examined: Kalamazoo Co. (H. Oosting,1926); Ingham Co. (H. Oosting,1926); Clinton Co. (H.T. Darlington, 1918); Iosco Co. (H.T. Darlington,l918); Gogebic Co. (H.T. Darlington). POTAMOGETON AMPLIFOLIUS Tuckerm. (large-leaved). General thruout. Frequent. Mostly in lakes, depths up up to 2 1/2 meters. Often without floating leaves. Largest submerged leaves in the genus, usually incrusted with lime. Fruiting July, August. Specimens examined: Berrien Co. (C.K. Dodge & H.T. Darlington,l9l7)° Lenawee 00. (H. Stocking); Kalamazoo Co. (E.B‘.Mains,19l3); Jackson Co. (3.3. Camp,1897); Washtenaw Co. (F.L. Stearns,l920); Wayne Co. (C. Billington, 1915); Ingham Co. (C.F. Wheeler,l900); Ottawa Co. (H. Oosting,1926); Kent Co. (C.W. Fallas, 1881); St. Clair Co. (C.K. Dodge,1895); {outcalm Co. (C.F. Wheeler,1900); Gratiot Co. (C.A. Davis,1893); Newaygo Co. (H. Oosting, 1926); Oceana Co. (D. Cooley 1850); Arenac Co. (?); Iosco Co. (C.F. Wheeler,1888 ; Roscommon Co. (E.A. Bessey, 1925); Charlevoix Co. (C.F. Wheeler,1894); Gogebic Co. (H.T. Darlington,l919). Reported from: Calhoun Co. (C.F. Barr,1908)-1Macomb Co. (E.J. Hill); Mhskegon Co. (v.0. Graham,l921 ; Huron Co. (C.A. Davis,1907); Mason Co. (E.J. Hill); Cheboygan Co. (Gates & Ehlers)‘ Schoolczaft Co. cc.K. Dodge,1921); Marquette Co. (C.K. Dodge). POTAMOGETON EPIHYDRUS Raf. (living on the water) or (upon the water). ".2. claytonii Tuckerm. .2; penns lvanicus Willd. P. nutta Iii C.‘& S. Frequent thruout. Lakes and streams. Commonly without floating leaves in running water. In swiftly flowing streams submerged leaves much elongated. In quiet water 5. 6. 3O submerged leaves have characteristic fan-like arrangement. Fruiting July, August. Specimens examined: Kalamazoo Co. (H. Oosting,1926); Hacomb Co. (D. Cooley,1840); St. Clair Co. (Miss N.P. Whiting,1894); Ottawa Co. (H. Oosting,1926); Mhskegon Co. (C.D. MbLouth,18999; MOntcalm Co. (H.T. Darlington,l919); Neway 0 Co. (H. Oosting,1926); Roscommon Co. (E.A. Bessey, 1916 ; Iosco Co. (H.T. Darlington,l918); Alpena Co. (H.T. Darlington,l918): Luce Co. (C.K. Dodge,19l5); Alger Co. (C.F. Wheeler,1895); Marquette Co. (C.F. Wheeler,1892); Gogebic Co. (H.T. Darlington,l918); Keweenaw Co. (O.A. Farwell,1888). Reported from: Oakland Co. (C.A. Davis,1907); Tuscola Co. CC.K. Dodge,1921); Chippewa Co. (C.K. Dodge,1921); Schoolcraft Co. (C.K. Dodge,1921). POTAMOGETON ALPINUS Balbis. (alpine). Infrequent. Distribution general. Entire plant suffused with reddish tinge. Fruiting July, August, September. Specimens examined; Macomb Co. (A.J. Pieters,1893); Kent Co. (C.W. Fallas,1897); Charleveix Co. (C.W. Fallas, 1918); Emmet Co. (J.H. Ehlers,l922); Bois Blane Island, (S.H. Camp,1894); Alger Co. (C.F. Wheeler,1900); Marquette Co. (C.F. Wheeler,1892); Gogebic Co. (E.A. Bessey,l919); Keweenaw Co. (0.A. Farwe11,l888); Isle Royals. (A.E. Foote,l868); Reported from: Wayne Co. (0.A. Farwell,l900); Cheboygan Co. (Gates & Ehlers). POTAMOGETON AMERICANUS C. & S. P. lonchites Tuckerm. mluitans Roth. Common. Distribution general. Slow streams and also lakes and ponds. Depths up to 3 meters. 0ften.without floating leaves and sometimes with floating leaves only, the large, delicate submerged leaves being broken up by 1 7. 8. 31 the water movements. Calcium incrustation common. Fruiting July, August. Specimens examined: Berrien Co. (H.T. Darlingtoh, 1919); Cass Co. (H.S. Pepoon,l904); Lenawee Co. (C. .Iflllington,l914); MOnroe Co. (B.A. Walpole,l920); Kalamazoo Co. (E.B. Mhins,l9l3); Calhoun Co. (W.J. Beal, 1898); Jackson Co. (S.H. & D.R. Camp,1893); Wahhtenaw Co. (F.L. Stearns,l920); Barry Co. (H. Oosting,1926); Livingston Co. (F.L. Stearns,l920); Macomb Co. (C.F. Wheeler,l900); Ottawa 00. (H. Oostin ,1926); Shiawasee Co. (G.H. Hicks,1890); Montcalm Co. (C.F. Wheeler,1900); Newaygo Co. (H. Oosting,1926); Huron Co. (C.A. Davis). Reported from: Wayne Co. (O.A. Farwell); St. Clair Co. (A.J. Pieters,1894); Muskegon Co. (O.A. Graham,1921); Bay to Cheboygan Co.,frequent thruout,(C.H. Dodge,1921); Manistee Co. (F.P. Daniels); Keewenaw Co. (O.A. Farwell, 1904). POTAMOGETON FAXOHI Morong. (named for C.E. Faxon). Gray's Manual, 7th edition, - infertile hybrid of P. alpinus. Previously discussed. Status doubtful. Specimens examined: Jackson Co. (S.H. Camp,1897); Genesee Co. (D. Clark). POTAMOGETON'HETEROPHYLLUS Schreb. (variously leaved). Distribution general. Very Common. Extremely variable. Without floating leaves in rough water. Ordinarily the plants are found growing in a series Connected by the rootstock. Fruiting July, August, September. Specimens examined: Van Buren Co. (H.S. Pepoon, 1906); Kalamazoo Co. (H. OOsting,l926); Jackson Co. (S.H. Camp,1897); Washtenaw Co. (F.L. Stearns,l920); Ingham 00.; Liningston Co. (F.L. Stearns,l920); Oakland Co..(C. Billingtcn,l916); Macomb Co. (A.J. Pieters,1893); Ottawa Co. (H. Oosting,1926); Kent Co. (L891); Clinton Co. (H.'I'. Darlington,l918); St. Clair Co. (C.K. Dodge,1904); Montcalm Co. (C.F. Wheeler,l900); Newqygo Co. (H. Oosting, 1926); Lake Co. (W.J. Beal,1890); Huron Co. (C.A. Davis, 1896); Missaukee Co. (E.A. Bessey,l9l6l; Iosco Co. (C.F. Wheiler,1888); Grand Travers Co. (18881; 32. Alcona Co. (1888); Charlevoix Co. (C.F. Wheeler,1892); Cheboygan Co. (F.C. Gates,l9ll); Emmet Co. (G.H. Fallas, 1897); St. James Island, (C.W. Wheeler, 1900); Alger Co. (C. Billington,l9l6); Harquette Co. (A. Dachnowski,l906); - Gogebic Co. (H.T. Darlington,l919); Ontonagon Co. (E.A. Bessey,1923); Keweenaw Co. (O.A. Farwell,1888); Isle Royale, (A.E. Foote,1868). Reported from: Cass Co. (H.S. Pepoon,l907); Wayne Co. (O.A. Farwell,1900); Tuscola CO. (C.K. Dodge,1921); Huskegon Co. (v.0. Graham,1921); Chippewa Co. (C.K. Dodge,» 1921); Schoolcraft Co. (C.K. Dodge,1921). 9. POTAHOGJTOH VARIAHS Korong. (variable). Infrequent. Distribution probably general, previously discussed. Closely resembles P. heterOphyllus and has characteristics of several other Species. Fruits July, August. Specimens examined: Kacomb Co. (A.J. Pieters,1893); Ottawa Co. (H. Oosting,1926); Montcalm Co. (C.F. Wheeler, 1900); Cheboygan Co. (H.C. Beardslee,1690); Hackinaw Co. (S.H. & D.R. Camp,1824); Keweenaw Co. (0.1. Farwell,1888). 10. POTARCGETON ILLIN ENSIS Morong. Two specimens collected and identified by McLouth and Walpole are doubtful. Both are immature and lack fruits. No other record or collections found in the state. Specimens examined: Huskegon Co. (C.D. NcLouth,l894); Allegan Co. (B.A. Walpole,1923). ll. POTAKOGZTOH AHGUSTIFOLIUS Berch. & Presl. (narrow- leaved). P. zizii Roth. Distribution general. No Specimens or rec0rds from _BppEr Peninsula. Common. Very prolific in some areas. Fruiting July, August. 33 Specimens examined: Berrien Co. (H.T. Darlington, 1917); Kalamazoo Co.(H. Oosting,1926); Washtenaw Co.(1838); Ingham Co. (Wheeler & Hicks,1893); Livingston Co. (F.L. Stearn8.1920); Hacomb Co. (A.J. Pieters,1893); Clinton Co. (1884); Kent Co. (A.J. pieters,1897);‘Muskegon Co. (C.D. MbLouth,1890); Mbntcalm Co. (C.F. Wheeler,l900); Huron Co. (C.K. Dodge,1908); Iosco Co. (H.T. Darlington,l918); Charlevoix Co. (C.F. Wheeler,l892); Cheboy an Co. (C.F. Wheeler 1890); Emmet Co. (J.H. Ehlers,l921 ; Bois Blane Island (1894). Reported from: Nanistee Co. (E.J. Hill); Wayne Co. (D.H. Campbell); St. Clair Co. (A.J. Pieters,1893). 12. POTAMOGETON LUCENS L. (shining). Distribution general. Common in lakes and ponds. Usually may be distinguished by its large shining leaves. Fruiting July, August. Specimens examined: Cass Co. (H.S. Pepoon,l904); Van Buren Co. (L.H. Pennington,1910); Kalamazoo Co. (H. Oosting,1926); Washtenaw Co. (Miss G. Williamson,1901); Ingham Co. (C.F. Wheeler,l900); Livingston Co. (F.L. Stearns,l900); Oakland Co. (B.A. Walpole,1920); Hacomb Co. (A.J. Pieters,1893); Clinton 00. (H.T. Darlington,l918); Kent Co. (A.J. Pieters,1897); Ottawa Co. (H. Oosting,1926); Newaygo Co. (H. Oosting,1926); Iesco Co. (H.T. Darlington, 1918 ; Cheboygan Co. (F.C. Gates,l9ll); Emmet Co. (C.W. Fallas,1897); St. James Island (C.F. Wheeler,1900). Reported from: Wayne Co.(D.H. Campbell); Huskegon Co. (C.D. MbLouth); Chippewa Co. (C.K. Dodge,1921). 13. POTAMDGETON PRAELONGUS Wulf. (very long). Distribution general. Common in deeper ponds and lakes, depths of 2 to 4 meters. Flowers at surface. Stem.contracts drawing fruits to deep water where they mature. Large and coarse, can be recognized by the white stems and the large white stipules. Fruiting July, August. 14. 34 Specimens examined: Cass Co. (H. S. Pepoon, 1906); Van Buren Co.(F. Gates ,1906); Kalamazoo Co.(E.B. Mains, I913); Jackson Co.(S. H. Camp,1897); Washtenaw Co. (F. L. Stearns ,1920); Ingham Co. (C. F. Wheeler,l900); Clinton Co.(H. T. Darlington, 1900); Ottawa Co. (H. Oosting,1926); Gratiot Co. (C.A. Davis,1895); Mbntcalm Co. (C. F. Wheeler,l900); Newaygo Co. (H. Oosting,1926); Iosco Co. (H.T. Darlington, 1918); Cheboygan Co. (F.C. Gates,l9ll); Gogebic Co. (H. T. Darlington, 1919) Ontonagon Co. (H. T. Darlington,,E. A. Bessey,l923). Reported from: Oakland 00. (C.A. Davis,1907)' Kent Co. (Emma J. Cole,1901); Emmet Co. (Fallas and Swift, 1918 . POTAKOGETON PERFOLIATUS L. (thru the leaf, or clasping). P. riehardsonii Rydb. Distribution general. Very common. Water upt to a meter in depth. Prolific. Leaves variable, orbicular to linear-lanceolate. May be distinguished from small specimens of P._praelongus by absence of white stipules and by the perfoliate base. Fruiting July, August. Specimens examined: Berrien Co. (H.T. Darlington, 1917); Kalamazoo Co. (H. Oosting,1926); Monroe Co. (B.F. Chandler, 1914); Wahhtenaw Co. (Miss H.W. Thompson,l903); Wayne Co. (C. F. Wheeler ,1892); Barry Co. (H. Oosti , 1926); INgham Co. (C. F. Wheeler,l900); Oakland Co.n%C. Billington, l9l5L Macomb Co. (A. J. Pieters ,1893L St. Clair Co. (A. J. Pieters,1893); Ottawa Co. (H. Oosting, 1926); muskegon Co. (C. D. McLouth,l894); Mbntcalm Co. (H. T. Darlington, 1917); Gratiot Co. (C. A. Davis 1893); Newa go Co. (H. Oosting,1926); Huron Co. (0. K. Dodge, 1908); Iosco Co. (W. J. Beal & C. F. Wheeler ,1888); Antrim Co. (0. W. Fallas ,1920); Charlevoix Co. (H.D. Thompson, 1894); Cheboygan Co. (F. C. Gates 1911); Emmet Co. (J.H. Ehlers ,1921); Alger Co. (C. F. Wheeler, 1900); Marquette Co. (A. Dachnowski,1906); Gogebic Co. (H.T. Darlington, 1919); Isle Royals (A. E. Facts 1861); Kent Co. (J. Shadduck ,1896) . Reported from: Case Co. (HB S. Pepoon, 1907); Van Buren Co. (H.S. Pepoon, 1907); Co. (G. M". Bradford); Schoolcraft Co. (C. K. Dodge, 1921 . 55 15. POTAMOGETON CRISPUS L. (curly). Three stations in Ottawa 00., one in Van Buren Co. A European species, established on the coast and migrating west along the watercourses. Leaves crisp and have margins crimped. Grows the year around. Not collected in fruit but winter buds usually present. Specimens examined: Van Buren Co. (L.H. Pennington, 1910); Ottawa Co. (H. Oosting,1926). 16. rorm‘zocsrom COIZPRESSUS L. (flattened stem). P. zosteraefolius Schum. Very Common. Distribution general thruout. Streams, ponds and lakes. In running or exposed water or in standing water. Collected at all depths up to 2 or 3 meters. Fruiting July and August. Specimens examined: Berrien Co. (H.T. Darlington, 1917); Van Buren Co. (D.A. Pelton,1880); Kalamazoo Co. (H. Oosting,1926); Lenawee Co.(C.H. Stocking,1861); Washtenaw Co. (W.H. Rush,189l); Barr Co. (H. Oosting, 1926); Ingham Co. (C.F. Wheeler,l892 ; Livingston Co. (F.L. Stearns,l920); Oakland Co. (B.A. Walpole,l9l9); Macomb Co. (A.J. Pieters,1893); St. Clair Co. (C.K. Dodge,1904); Ottawa Co. (H. Oosting,1926); Kent Co. (A.J. Pieters,1897); Clinton Co. (H.T. Darlington,l918); Gratiot Co. (C.A. Davis,1898); Montcalm Co. (C.F. Wheeler, 1900); Newaygo Co. (H. Oosting,1926); Iosco Co. (WJ Beal, & C.F. Wheeler,1888); Oscoda Co. (H.T. Darlin ton,l918); Cheboygan Co. (F.C. Gates,l9ll); Gogebic Co. H.T. Darlington,& E.A. Bessey,l9l8). Reported from: Cass Co. (H.S. Pepoon,l907); Wayne Co. (B.A. Farwell,l900); Muskegon Cal (C.D. MbLouth,1896); Emmet Co. (Gates & Ehlers); Marquette Co. (C.K. Dodge, 1918 . 36 17. POTAMOGETON HILLIIZMorong. (named for Hill). Probably general. At least in the Southern Peninsula. Infrequent. Sometimes found without glands at leaf bases but is easily recognized by the characteristic fruits. Fruiting July and August. Specimens examined: Kalamazoo Co. (H. Oosting,1926); Ottawa Co. (H. Oosting,1926); Kent Co. (A.J. Pieters,1897); St. Clair Co. (C.K. Dodge,1896); Neway 0 Co. (H. Oosting, 1926); Manistee Co. (D.A. Pellton,1884 . 18. POTMTOGETON FOLIOSUS Raf. (leafy). Occasional. Distribution general. In shallow water, lakes and streams. In fruit it can be identified at 'once by the irregular characteristic keel on the back. Fruiting July, August. Specimens examined: Berrien Co. (C.K. Dodge, H.T. Darlington,1917); Cass Co. (H.S. Pepoon,lQO4); Van Buren Co. (L.H. Pennington,l9lO); Kalamazoo Co. (S.H.Wolff, 1924); Washtenaw Co. (F.L. Stearns,lQZO); I gham Co. (H.T. Darlington,l918); Ottawa Co. (H. Oosting,1926); Ionia Co. (C.F. Wheeler,1881); Genesee Co. (D. Clark); ‘Montcalm Co. (C.F. Wheeler,l900); Iosco Co. (W.J. Beal & C.F. Wheeler,1888); Manistee Co. (E.J. Hill,l880); Marquette Co. (A. Dachnowski,1906); Keweenaw Co. (O.A. Farwell,1886). ' l9. POTAMOGETON FRIESII Ruprecht. (named for E. Fries). P. mucronatus Mann. Distribution general. Frequent. Upper Peninsula distribution doubtful. Collected commonly in shallow, \ quiet water with mucky bottom. Fruiting July, August. 37 Specimens examined: Kalamazoo Co. (H. Oosting,1926); Jackson Co. (C.F. Wheeler,1898); Washtenaw Co. (G.H. Kaufman,1923); Ingham Co. (C.F. Wheeler,1900); St. Clair Co. (W.S. Couper,l90l); Ottawa Co. (H. Oosting,1926); .Montcalm Co. (C.F. Whehler,l900)° Newaygo Co. (H. Oosting, 1926); mason Co. (C.E. Barr,19m9 ; Manistee Co.(E.J. Hill, 1880); Arenac Co. (C.F. Wheeler,1900); Iosco Co. (W.J. Beal & C.F. Wheeler,l888); Antrim Co. (C.W. Fallas,1920); Emmet Co. (0.]. Fallas,1921). Reported from; Wayne Co. (O.A. Harwell); Oscoda Co. (E.J. Hill); Cheboygan Co. (E.J. HIll). 20. POTAMOGETON OBTUSIFOLIUS Mert. & Koch. (blunt-leaved). One station only, but Specimen agrees perfectly with available descriptions. fruiting August. Specimen examined: St. Clair Co. (C.K. Dodge,1904). 21. POTAMOGETON RUTILUS Wolfg. (reddish-yellow). Distribution general in south and probably thruout. Occasional. Prepagating buds often absent. Fruiting July and August. Specimens examined: Van Buren Co. (H.S. Pepoon, 1904); Jackson Co. (S.H. Camp,1896); Monroe Co. (B.A. Walpole,l920); Wayne Co. (C.F. Wheeler,1892); Oakland Co. (B.F. Chandler,l916); Kent Co. (W.E. MDlliken,1896); Marquette Co. (A. Dachnoski, 1906). 28. POTAKOGETON VASEYI Robbins. (named for Vasey). One station only. Probably no more because the Species is not recognized. Commonly grows without floating leaves and fruits rarely. August. Specimen examined: St. Clair Co.(C.K. Dodge,1896). 38 23. POTAMOGETON PUSILLUS L. (very small). Very common. General thruout. Ponds and shallow, slow streams at depths from 1/2 to 2 meters. Variable in general form but glands, buds and fruits invariable. This is one of the commonest species. Fruiting July and August. Specimen: examinedi Cass Go. (H.S. Pepoon,l904); Kalamazoo Co. (H. Oosting,1926); Washtenaw Co. (W.H. Rush,189l); Ingham Co. (C.F. Wheeler,1892); Oakland Co. (B.A. Walpole,1920); Mgcomb Co. (A.J. Pieters,1892); ST. Clair Co. (W.S. Cooper,l903); Ottawa Co. (H. Oosting, 1926); Kent Co. (W.E. Mulliken,1896); Newaygo Co. (H. Oosting,1926); Iosco Co. (H.T. Darlington,l918); Alpena Co. (C.F. Wheeler,l895); Cheboygan Co. (J.H. Ehlers, 1921); Emmet Co. (C.W. Fallas,1918); Marquette Co. (C.K. Dodge,1916); Gogebic Co. (H.T. Darlington,lQlB); Reported from: Van Buren Co. (H.S. Pepoon,1907); Wayne Co. (D.H. Campbell); Muskegon Co. (E.A. Bessey, 1920); Manistee Co. (EQJ. Hill); Chippewa Co. (C.K. Dodge,1921); Schoolcraft Co. (C.K. Dodge,1921). 24. POTAMOGETON FILIFORMIS Pers. (thread-like). Distribution general. Frequent. Shallow, quiet water. This is one of the most delicate epecies and can be recognized in the field by its filiform structure. Fruiting July, August. Specimens examined: Kalamazoo Co. (E.B. Mains); Macomb Co. (A.J. Pieters,1893); St. Clair Co. (C.K. Dodge,1904); Ottawa Co. (H. Oosting,1926); Montcalm Co. (C.F. Wheeler,l900); Huron Co. (C.D. Davis,1896); Iosco Co.(H.T. Darlington,l918); Missaukee Co.(C.W. Fallas, 1897); Charlevoix Co. (H.S. Jennings,1894); Cheboygan Co. (J.H. Ehlers,lQZl); Chippewa Co. (B.A. Pellton,1881); Gogebic Co. (H.T. Darlington,lQlQ). Reported from; Wayne Co. (O.A. Farwell); Emmet Co. (Gates & Ehlers). 39 25. POTAMOGETON INTERIOR Rydb. (inland). Common. Distribution general. Shallow, warm.water. Should be collected in fruit to distinguish it from (26). Fruiting July, August, September. Specimens examined: Kalamazoo Co. (H. Oosting,1926); Jackson Co. (S.H. Camp,1897); Barry Co. (H. Oosting, 1926); Macomb Co. (A.J. Pieters,1893); Ottawa Co. (H. Oosting,1926); Newaygo Co. (H. Oosting,1926); Antrim Co. (C.W. Fallas,1920); Charlevoix Co. (C.F. Wheeler,1892); Eggs? Co. (J.H. Ehlers,lQZZ); Gogebic Co. (H.T. Darlington, 26. POTAMOGJTON PECTIHATUS L. (comb-like). Very common. General thruout. Shallow, warm water, ponds and lakes. Is commonly a little smaller than (25). and has the appearance of a fan-like comb in the water. Fruiting July, August and September. Specimens examined: Berrien Co. (C.K. Dodge & H.T. Darlington,l9l7); Cass Co. (H.S. Pe oon,l904); Kalamazoo Co. (H. Oosting,1926); Jackson Co. (S.H. & D.R. Camp); Lenawee Co. (D. Cooley,1858); Washtenaw Co. (W.H. Rush, 1891); Wayne Co. (C. Billington,l9l5); {aflomb Co. (A.J. Pieters,1893); Oakland Co. (C. Billington,l915); Macomb 00.; Livingston Co. (F.L. Stearns,l920); Ingham Co. (C.F. Wheeler,l892); Barry Co. (H. Oosting,1926); Ottawa Co. (H. Oosting,1926); Kent Co. (A.J. Pieters,1897); Clinton Co. (H.T. Darlington,l918)- Genesee Co. (D. Clark); St. Clair Co. (C.K. Dodge,1904); Muskegon Co. (C.D. McLouth, 1904); Newaygo Co. (H. Oosting,1926); Midland Co. (R.R. Driesbach,1918); Bay Co. (W.J. Heal w C.F. Wheeler,1888); Roscommon Co. (H.T. Darlington,l9l6); Manistee Co. (E.J. Hill,l872¢; Cheboygan Co. (F.C. Gates,lQll). 27. POTAMOGSTON INTERRUPTUS Kitaibel. (interrupted, referring to the mode of growth). Rare but distribution general. Stations in the North, East and lest. Rarely found in fruit. 40 Specimens examined: St. Clair Co. (C.K. Dodge,1893); Cheboygan Co. (C.F. Wheeler,1880); Manistee Co. (E.J. Hill). 28. POTAMOGBTOH ROBBIHSII Cakes. (named for Robbins). Four stations in Southern Peninsula and one in the flpper Peninsula. Probably more general but not recognized. If P. epihydrus is without floating leaves, the two are very similar in the water because of the Opposite branching, forming a fan. P. epihydrus has longer leaves and does not send a long fruiting stem up to the surface. It also lacks the serrate margins of the leaves. Specimens examined: Washtenaw Co. (F.L. Stearns, 1920); Ingham Co. (C.F. Wheeler,189l); Ottawa Co. (H. Oosting, 1926); Muskegon Co. (E.J. Hill, 1899); Marquette Co. (A. Dachnowski, 1906). BIBLIOGRAPHY (1) ARBER, Agnes. 1919. Aquatic AngiOSperms. Hot. Gas. 51: 83-86. (2) ------------ 1920. Water Plants. xvi'O436. 171 figs. Cambridge University Press, London. (3) SBENETT, A. 1889. Synonymy of P. Zizii. Jour. Bot g1: 263 - 264. (4) .......... . 1890. Nomenclature of Potamogeton. Jour. B015. PE: 3010 (5) ---------- . 1907. Two Japanese Potamogetons. Jour. Bot. 45: 233. (6) —————————— . 1907. Forms of Potamogetons new to Great Britain. Jour. Bot. 45: 172. (7) .......... . 1918. Notes on H5gstrom's "Critical Researches on Potamogetons." Trans. & Proc. Bot. Soc. Hdinburgh 21: 315-326. (8) —————————— . 1919. Notes on British Potamogetons. Jour. Bot.§Z: 10-20. P. acutifolius. Jour. Bot. 57: 101. P. dualis. Jour. Bot.,§1: 285. (9)' .......... . 1924. Notes on Potamogetons. Trans. & Proc. Bot. Soc. 3dinburgh 22: 46-51. (10) --------- . 1927. Notes on Potamogetons. Jour. Bot. 65: 113-116. ”" (ll) BERRY, E.W. 1921. A Potamogeton from the upper Cretaceous. American Jour. Sci. lg 420-423. (12) BOWKAN, H.H.M; 1921. The development and activation of Hibernacula. Papers Mich. Acad. Sci: 1: 62 - 74. Pl. 26-29. (15) BRITTON, N.L. a A?" BROWN. 191M Illus rated Flora of the Northern States and Canada. 3 vols. . Charles Scribner's Sons. New York. (14) CAMPBELL, D.H. 1896. Plants Of the Detroit River. Bull. Torrey Bot. Club 13; 93. (14a) COULTER,BARNES & COWLES. 1911. A Textbook of Botany. Vol.2. Cowles, H.C. Ecology. x-r964. Illustrated. Am. Book CO. New York. (15) COHITER, J.M; 1917. Review of Hégstrom. Bot. Gaz. pg: 87 -88. (16) DACHNONSKI, A.P. 1912. Succession of vegetation in the Lakes and Peat Deposits of Ohio. Geol. Surv. Ohio, 4th. series, Bull. 16. villa-423. 8 P1., 29 fi s. (17) DAVIS, C.A. 1906. Peat. Geol. Surv. Mich. Ann. Rep. 1-361.‘Pl._14-31. figs. 1-19. (18) EMERSON, F.W. 1921. Subterranean Organs of Bog Plants. Bot. Gaz. 12: 359-374. figs. 1-11. ' (19) FERNALD, 1231;. a 3.1.. Robinson. 1908. Gray's New Manual of Botany.,7th. edition. 42 926 pgs. illustrated. Am. Book Co., New York. (20) FRYER, A. 1888. Notes on Pondweeds. Jour. Bot. 26: 273 - 278. (20a) -------- 1889. Notes on Pondweeds. Jour. Bot. 27: 65 -67. (21) GATES, F.C. 1911. Vegetation of the region in the vicinity of Douglas Lake, Cheboygan Co. ‘Mich. Mich. Acad. Sci. Rep. 14: 46-102. (22) GODhIN, H. 1923. DiSpersal of Pond Floras. Jour. Ecol. 1: 160 -164. 2 fi 8. (23) GOE,L.,E. ERIC SON & E. WOOLETT. 925. Ecological study of Mud Lake Bog in Cheboygan CO., Mich. Papers Mich. Acad. Sci. 35 297- 310. figs. 4- 7. (24) HALE, D.J. 1903. Mar1(Bog LimeT_ Geol. Surv. Mich.f§5 part 3: 1-101. (25) HALFE TY, G.M. 1901. Ovule and Embryo of PotamOgeton. Bot. Gas. 31: 339-346. 1 fi . 2 P1. (26) HANKINSON, E.L. 1907. Biblogical Surve§*6§‘walnfit Lake, Mich. Geol. Surv. Liich. Ann Rep. (The Flora-C. A. Davis) 217- 231. (27) HASTINGS, G.T. 1924. Water plants of the Kanawauke bakes. Torreya 24:93-97. (28) HILL, E.J. 1898. P. Robbinsii. Bot. Gas. 25. 195 - 196. P1. 15. (29) HOPKINS, L.S. 1919. Occurrence and distribution of Vasey's pondweed in Northeastern Ohio. Torreya 1g: 243-244. (30) HULL, E.D. 1913. Advance of P. criSpus L. Rhodora: 15: 171-172. (31) LORI, F.A. 1915? Role of Vegetation of a Millpond. Mich. Acad. Sci. Rep. 15: 201 - 204. 3 fi 3. (32) MAGNIN, A. 1893. P§ants of the lakes of the Jura. Nat. Sci. 5; 248. (33) MC ATEE, W.L. 1915. Eleven important Duck Foods. U.S.D.A. Bull. 205: 1-25. 22 figs. (33a) ----------- . 1917. PrOpagation of Wild uc Foods. U.S.D.A. Bull. 465: 1-40. 35 fi 8. (33b) ----------- . 1920. Waterfowl and their 00 p ants. U.S.D.A. Bull. 794: 1-77. 4 P1. (34) MOORE, EMMELINE- 1913. The Potamogetons in relation to Pond Culture. U.S. Bureau Of Fisheries Bull. a: 251- 2910 Pl.22-39. (35) MORONG, T. 1892. The Naiadaceae of North America. Mem. Torrey Bot Club. 3:1-65. P1. 20 - 74. (36) NEEDHAM; J.G. 1921. A‘biological examination of Lake ' George, N.Y. Sci. Monthly 12: 434-438. (37) PALLADIN, 7.1. 1926. Palladin's Plant Physiology, 3rd (38) (39) (40) (41) (42) (45) (44) (45) (46) (47) (48) (49) (50) (52) (530 43 American edit. Transl. BoE. Livingston. mum-0360. 173 f1 s. W.H. 1919 Hagstrom's critical researchs on Potamogeton. Bot. Soc. & Exchange Clug British Isles. Rep. 5: 701- 713. ---------- . 1923. Potamogetons in the English Lakes. Jour. Bot. 61: 1. . 1925. Variation in Leaf form of P. perfoliatus. New Phytol. 24: 112-120. PENNINGTON, L. H. 1906. Plant Distribution in Mud Lake. Mich. Acad. Sci. Rep.‘§,: 54 - 63. fi 8 1-4. PIETERS, A.J. 1894. Plants of Lake St. EARSALL, Clair. Biennial Rep. State Board of Fish Comm. 11, Bull. fig 1-10. ---------- . 1901. The Plants of Western Lake Erie with observations on their distribution. U13. Fish. Comm. Bull. 21: 57-79. POND, R.H. 1918. The larger Aquatic Vegetation, in Ward & Whipple, Fresh Water Biology. Chap. 7: 178 -209. figs. 254-273. REED, H.S. 1902. Ecology of a Glacial Lake. Bot. 34: 125 - 139. 4 fi 3. RICKETT, H.W. 1924. A quantitative study of the larger aquatic plants Of Green Lake, Wisc. Trans. Wisc. Acad. Sci. 21: 381 - 414. Harold. 1916. A revision of the North Am American species of Potamogeton of the section Coleophylli. Rhodora 18: 121 - 138. 1924. Flora of Epsom Lake. Amer. Jour. 801$. 11: 100 - 1070 1925.“: critical consideration of Hagstrom's work on Potamogeton. Bull. Torrey Bot. Club. 52: 461 -471. 1 fig. S. 1925. Potamogetons of higher altitudes. Jour. Bot. 63: 141 - 142. TITCOMB, J.W. 1923. Aquatic plants in pond culture. U.S. Bureau of Fisheries. Doc. 948. VAN HISE, C.R. 1904. Metamorphism. U.S. Geol. Surv. Monograph 47, Vol. 2: 409 - 1284. Gage ST. JOHN, THOMPSON, H. \ url'v'd‘r- ~ - . . M11 HIGAN §TATE LIB" AF‘ |lllllllll||||l| 31293 01873 4883