108 The American Naturalist. [February, 
bees turn head downwards and hang upon the beards of the 
lateral petals while they collect the falling pollen. The violets 
also have an important pollinator in Andrena viole of the 
spring group of Andrena (Fig. 35, Plate X). The swamp rose- 
mallow (Hibiscus lasiocarpus, Fig. 6a, Plate VIII) has a bloom- 
ing time correlated with the time of flight of a characteristic 
American beé (Emphor bombiformis, Fig. 6b, Plate VIII), its 
principal pollinator ; the bee in turn depending on the Hibiscus 
for its pollen. Another interesting case of correlation in appear- 
ance and mutual dependence is, that of an alum-root (Heuchera 
hispida Fig. 11a, Plate VIII) and a little bee (Colletes aestivalis, 
Fig. 11b; Plate VIII). 
Returning to the Leguminosae (Fig. 15, Plate VIII) we 
observe that of the species which form the August maximum all 
are adapted to the most intelligent of the highest specialized 
genera of bees. Quitea number are bumble-bee flowers. The 
ordinary flowers have the stamens declined to the lower side 
and are best fitted to be pollinated by the leaf-cutter bees (Fig. 
32, Plate IX), which have abdominal brushes for collecting 
pollen, and I think that the position of the family in general 
should be regarded as associated with the flight of these bees. 
Two species adapted to bumble-bees, a ground plum (Astraga- 
lus mexicanus) and a false indigo (Baptisia leucophaea), occur 
early, which they may do without going out of the range of 
bumble-bees (Fig. 30, Plate IX) and they each gain an advan- 
tage by avoiding competition with a late blooming congener 
also depending upon bumble-bees. But no other ordinary 
papilionaceous flower blooms out of the flying time of the leaf- 
cutter bees. The very earliest of the family, the red-bud 
(Cercis canadensis) has the stamens declined to the lower side 
of the flower, so that the pollen is easily gathered by the mason 
bees (Fig. 31, Plate IX), which we have already mentioned as 
having abdominal brushes, like the leaf-cutters (Fig. 32, Plate 
IX), but fly early. The early appearance of the red-bud seems 
to be influenced by the early flight of these bees, though it is 
not exclusively visited by them. Finally, therefore, with 
regard to the blooming phenomena of the Choripetalae, we 
close with the propositions that the early preponderafice of the 
