Plant I, 6_r_ buds, 3_l_ buds, 2_r_ flowers, 5_l_ flowers.
II, 2_r_ " 1_l_ " 2_r_ " 0_l_ "
III, 1_r_ " 2_l_ " 2_r_ " 2_l_ "
IV, 2_r_ " 4_l_ " 2_r_ " 2_l_ "
V, 0_r_ " 1_l_ " 3_r_ " 1_l_ "
VI, 0_r_ " 0_l_ " 3_r_ " 2_l_ "
VII, 1_r_ " 3_l_ " 2_r_ " 2_l_ "
VIII, 1_r_ " 0_l_ " 1_r_ " 2_l_ "
IX, 2_r_ " 3_l_ " 5_r_ " 4_l_ "
X, 3_r_ " 1_l_ " 2_r_ " 1_l_ "
—— —— —— ——
18_r_ buds, 18_l_ buds, 24_r_ flowers, 21_l_ flowers.
There seems to be no law governing the production of right-and
left-handed flowers on the opposite sides of the main axis of the
plant. Sometimes two right-or left-handed flowers will be produced
in succession on one side of the raceme, and sometimes right-and
left-handed alternate on the same side.
Concerning the method of pollination in _C. chamæcrista_, the writers
have not been able to thoroughly satisfy themselves. Todd says: “I
consider the following explanation most probable: In getting the
pollen, some grains are dropped on the incurved petal, and by it made
to adhere to points of the bee, and to such points in a right-handed
flower as will carry it to the stigma of a left-handed flower, and
_vice versa_.” Robertson[S] says: “The pollen, being thus forced out of
the terminal anther pores, falls either directly upon the bee or upon
the lateral petal which is pressed close against the bee’s side. In
this way the side of the bee which is to the incurved petal receives
the most pollen.... A bee visiting a left-hand flower receives pollen
upon the right side and then flying to a right-hand flower strikes the
same side against the stigma.”
It is very difficult to see just what takes place when the flowers are
visited by a large insect, but the writers have observed that when they
are visited by honey-bees, for instance, the insect supports itself by
hooking his left hind leg over the terminal, upturned portion of the
stigma in a right-handed flower, and the right leg in a left-handed
flower. The pistil then would serve the function of support for the
insect visitor. It was noticed that sometimes bees would attempt to get
the pollen by approaching the flower from some direction other than
that described above. The insect usually failed in this, and after one
or two unsuccessful endeavors would give up the attempt and support
itself by placing the leg over the terminal portion of the pistil
while it secured the pollen. The function of the incurved petal is
not perfectly clear. With an insect well dusted over with pollen
from both right-and left-handed flowers, it seems improbable that
cross-fertilization in any considerable number of cases should occur
from some grains dropped on the incurved pistil.
The writers are not sure that the insect in flying to another flower
strikes the tip of the pistil against the side, as stated by Robertson.
Certainly, in many cases, the insect, while collecting the pollen,
supports itself by placing one leg over the tip of the pistil. When
the leg bears a large mass of pollen, which is being stored there, it
seems hardly possible that the flowers could fail to be pollinated.
It might be suggested that, since the stamens for the most part point
in the direction of the incurved petal, the function of this petal is
to prevent access to the stamens, except in the cases in which the
insect supports itself by means of the pistil. While this seems to the
writers, at the present time, the most logical of the two functions so
far suggested, much more careful observation work must be done before
this point is finally decided. The petal may to a certain extent, in
connection with the pistil, serve as support for the insect. Todd and
Robertson observed only humblebees visiting the flowers. The writers
obtained:
_Apis mellifica_ Linn. Lake View, August 7. Seven specimens.
_Agapostemon texanus_ Cress. Lake View, August 7.
_Mellisoides bimaculata_ (St. Farg) Lepl. Lake View, August 7.
_Megachile petulans_ Cress. Lake View, August 7.
_Bombus separatus_ Cress. Lake View, August 7.
As in the case of _Solanum_, it will be seen that the collecting period
extended over a very short period of time. More search would doubtless
greatly increase the list.
Robertson reports the following species as collecting pollen: _Bombus
virginicus_ Oliv., _B. separatus_ Cress., _B. americanorum_ F., and _B.
scutellaris_ Cress.
August 28, when the blossoming season for _C. chamæcrista_ was almost
over, an examination of material from the above-named region was made
for the purpose of determining the number of seeds produced by a single
plant. Fifteen pods were selected at random from different plants and
the number of ovules counted. It was impossible to tell about the
number in each pod which were fully and normally developed seeds or
which would become such; consequently this factor is not taken into
consideration. The percentage of ovules which fail to develop is,
however, small. The number of seeds found to the pod is shown by the
following: