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III. BOTANY AND ZOOLOGY.

1. Sensitive Stigmas as an aid to cross fertilization of flowers; by Prof. W. J. BEAL, (Proc. Amer. Assoc., Buffalo.)-The
flowers of Martynia proboscidia, a plant sometimes raised in our
gardens for pickles, has flowers drooping at an angle of about
forty-five degrees. At the opening on the upper side are two flat
stigmas, curved back away from each other, exposing the surface
which is sensitive to pollen. Farther on are the four anthers, side
by side, with their cells placed end to end. The opening is just
large enough to take in the humble bee, or the common hive bee
will do as well.
I have been carefully watching the Martynia plants for several
weeks, since they have been in flower, every day and at nearly all
hours and sometimes several times a day. I have the plants in
four places, two of which are beds about four feet by ten. They
are among other beds of flowering plants which are freely visited
by various kinds of insects. I felt quite sure that the humble bee
transferred pollen on his back, because I found the stigmas covered with pollen and closed before night each day. I could not
contrive how else the pollen could be transferred. I began to fear
I should have to give it up. But, one morning about nine o'clock,
I saw a single humble bee pass from flower to flower on nearly
every specimen on one patch of plants. The visit lasted only a
few moments. All parts are quite sticky with glutinous hairs
which seem to annoy the bees very much. I have never seen but
one bee on the flowers of Martynia; she alighted on the spotted,
showy part of the corolla, and crawled, first hitting the stigmas.
One of the most interesting points is now to be explained. The
stigmas are sensitive to the touch, and close up in five to ten seconds; often before the insect is ready to back out of the flower.
If they are not quite closed at that time, the bee shuts them by
pushing her back against the back of one of the stigmas. The
lower lobe of the flat stigma next to the bee's back is the larger.
No pollen can be left as the insect retreats. A cross of pollen is
usually certain. If not very freely dusted with pollen the stigmas
open again in about fifteen minutes ; if well dusted I have known
them to remain closed afterward.
The single flat stigma of the iris, one on each of three sides of
the flower, has often been shown to be sure of cross-fertilization, if

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fertilized at all. Some years ago I examined hundreds of specimens as they were fertilized by bees. The stigma closes up after
it is covered with pollen. It is sensitive to the touch; perhaps
only slowly, but I think it moves back in a few seconds. I have
examined no specimens lately with special reference to this point.
The stigmas of Mimulus ringens are curved out like those of the
Martynia, and project beyond the anthers. I have seen small native Hymenoptera visit this plant, always crawling in with the back
down, although Mühler says in personate flowers the bees always
get their backs up as they pass in. The stigmas of this Mimulus
are slowly sensitive, closing in a few moments after they are
touched or well supplied with pollen. The stigmas of the Mimulus luteus and Mimulus moschatus, and likely other species, close
very quickly after being touched. Tecoma radicans and Tecoma
grandiflora and probably other species, are very much like Martynia in the peculiarities mentioned. I have not lately had the
opportunity of examining the flowers of the Bigonia or Catalpa
but I shall expect to find them cross-fertilized in the same way as
Tecomia aided by sensitive stigmas. Utricularia vulgaris, one of
our larger common bladderworts, has a yellow irregular flower
which considerably resembles that of the snap-dragon. The
stigmas act much as in Martynia. The lower lip of the stigma is
much the larger and when touched bends up close against the
upper lip of the corolla just under an arch-like projection. The
other nice adaptions for securing cross-fertilization are rather complicated and need not be given at this time.
Pinguicula is quite similar in structure to the Utricularia and
is likely sensitive in its stigmas, and fertilized in the same way.
All the stigmas which I have seen that are sensitive, stand with
one side toward the space visited by insects, and if there are two
together, the larger stigma comes next to the body of the insect.
-Buffalo Courier, Aug. 25, 1876.