
222 THE AMERICAN NATURALIST. [VoL. XXXVI. 
and obtain the nectar, and in their absence the flowers fail to set 
seed. Slight imperfections frequently permit flies and. butterflies 
to steal the honey without rendering any service in return ; and 
it has been suggested that the numerous species may be due to 
the efforts of the plants, metaphorically speaking, to remedy 
these defects. 
The inflorescence is mainly in heads and racemes, but the 
effect of the individual flower cluster is often magnified mani- 
fold by the massing of the plants. In worn-out fields the vetch, 
Vicia cracca, often takes entire possession of the soil, forming 
large patches of purple blue. Similar effects are attained by the 
clover and wild lupine. Of the 197 species in the northern 
states, 39 are white, 33 are yellow, 13 red, 88 purple, and 24 
blue. The predominance of blue and blue purple are believed 
to be due to the preference of bees for this color. The well- 
known experiments of Lubbock have shown that the honeybee 
can distinguish between colors. Scarlet, fire red, and all lurid 
colors are avoided by the honeybee. Blue, violet, and red are 
most attractive, followed by various shades of purple, yellowish 
white, and white. 
An examination of the genera in which more than two species 
occur shows that they are rarely monochromatic; one or more 
species are usually differently colored from the rest. In Bap- 
tisia three species are white, two yellow, and one blue; in Trifo- 
lium (clover), four species are white, three yellow, four red, and 
three purple; in Psoralea two species are white, six purple, and 
three blue; in Astragalus seven species are white, three yellow, 
twelve purple, and one blue; and in Meibonia (tick trefoil), two 
species are white, one red, and nineteen purple. It is probably 
more advantageous in these genera for a part of the species to 
be of one color and a part of another than for all to be blue. 
When species are closely allied bees tend to visit them indis- 
criminately, as may be observed in the buttercups and golden- 
rods. But even in these cases they exhibit a preference to keep 
to a single bom and would be greatly aided by differences in 
the coloring. 
. . Many of the flowers of the Papilionaceze i in fading undergo a 
change of position and color, in the white clover the white 
