1899] FLOWERS AND INSECTS 41 
receptive stigmas, because she instantly perceives that the anthers 
are gone. Apis mellificaand Bombus virginicus do the same when 
collecting the pollen of Z. falva. In Campanula Americana, which 
is also proterandrous, the oligotropic Megachile exilis cleans the 
pollen from the style-brushes before the stigma opens, and avoids 
the old flowers. In Lobelia syphilitica | have seen little bees col- 
lecting the pollen which was pushed out of the anther tube before 
the stigma appeared. Inthe proterandrous Monarda Bradburiana 
I have seen small bees collecting pollen directly from the 
anthers, avoiding the old flowers. The strongly dichogamous 
flowers mentioned in the table are not so well adapted to utilize 
their'special visitors as are the homogamous ones, such as Viola, 
. Psoralea, Hibiscus, Cassia, because in the latter the bees cannot 
collect the pollen without touching the stigmas. 
Some dichogamous flowers may make effective use of the 
pollen-collecting bees, as in the case of Nymphea reniformis, 
which, in my opinion, is proterogynous and without nectar. By 
a sudden bending of the filaments, bees alighting on the anthers 
are let down into the stigmatic basin before they discover that the 
pollen is not being discharged. Of course, in other dichogamous 
flowers the bees may visit the flowers in the pistillate stage before 
they discover that the pollen is gone, or for nectar, but my 
observations have convinced me that this is not the rule, for if 
they do not know exactly what they are doing and how to do it, 
they act just like it. On their pollen-collecting expeditions they 
do not make many mistakes or waste much time. 
Even some homogamous flowers are so-large that the smaller 
bees may collect their pollen without touching the stigmas. 
This may not matter so much if the flowers are visited by large 
bees, which are more effective. But the smaller flower may, in 
many cases, utilize the large bees as well and the smaller ones 
better, So I think the influence of the pollen-collecting bees is 
in favor of the smaller homogamous flowers. 
Under the influence of the nectar-sucking, less specialized, 
anthophilous insects the highest development is found in 
diclinous, dichogamous, and hercogamous flowers with highly 
