1879. | The Fertilization of Clitoria and Centrosema. 689 
closely applied to each other. The filaments (f) are united, 
excepting on the side next the vexillum. Within the base of the 
filaments is a large nectar gland (z), broken on the side next the 
standard, and slightly five-lobed on its free surface, suggesting its 
homology with a whorl of five stamens. Through the break 
on its lower side and the breaks in the tube formed by the fila- 
ments, the abundantly-secreted nectar flows into the basal part of 
the standard, and it is to this that the guiding marks of this petal 
lead. The pistil-consists of an elongated, stalked ovary (o) and a 
slender style terminated by an enlarged stigma (s¢), which usually 
protrudes slightly from the tip of the keel when the flower is 
expanded. 
From its structure it may be predicted that this flower is 
designed to be fertilized by bees, but though I have often care- 
fully watched dozens of plants growing together, for a long time, 
I have never seen a bee visit one of them, though I have some- 
times noticed a swiftly-flying black bee (Melissodes nigra) flying 
nervously among the flowers, and I have no doubt that this 
species, at least, visits them for their honey. Once I saw a but- 
terfly (Cadidryas eubule) standing on the keel and having its pro- 
boscis inserted between the bases of the keel and the wing petals, 
thus reaching the nectar at the base of the standard. To show 
what would happen if a bee entered the flower, we may insert the 
end of a small pencil between the vexillum and the tip of the 
keel. First of all this comes in contact with the stigma, and this 
would take up any pollen on its upper surface. Differently from 
what occurs in the majority of leguminous flowers, the rigid keel 
and standard do not readily move apart by a wedging action 
between them, but as we insert the pencil a little farther it 
encounters the wings on either hand and forces these apart lat- 
erally. In doing this the sides of the keel are slightly pulled 
apart, owing to their union with the wings, and the pollen col- 
lected in the keel is allowed to fall upon the pencil. That this is 
what occurs in nature when a bee visits the flower, I think there 
can be little doubt; though a set of collecting hairs (Fig. 1v, 4) 
on the inner side of the style makes it appear probable that the 
keel is forced somewhat upward, so as to cause these to pump 
out a quantity of pollen. In Central Alabama, where these ob- 
servations were made, a fair percentage of the flowers set fruit, 
but I am unable to say whether the plant is self-fertile or not. 
