438 Trans. Acad. Sci. of St. Louis 
wide as fifteen millimetres, but on account of the short and 
narrow petals they are far from showy. 
The stigmas become receptive before the anthers dehisce. 
The stamens are numerous, but short, and the outer ones dis- 
charge their pollen first. There is an opportunity for cross- 
pollination, for self-pollination by insects, and for spontaneous 
self-pollination in absence of insects. But the inner and 
upper stigmas can hardly receive pollen except by insect aid. 
The honey secreting ring between the outer pistils and inner 
stamens is more readily accessible than in R. villosus, on 
account of the stamens being shorter and Jess abundant. 
I have seen the flowers visited by Andrena bicolor F. 9, 
and Odynerus anormis Say. 
Rusus vittosus Ait. —The stems rise from one to two 
metres high and bear numerous white flowers, which expand 
horizontally from two to four centimetres. 
When the flowers first open, the numerous stigmas are 
receptive while the anthers are still closed. At this time, and 
_later, when the outer anthers are discharging their pollen, a 
bee entering the flower may readily effect cross-pollination. 
At the same time, insects coming without pollen may effect 
self-pollination. When the inner anthers dehisce, spontaneous 
self-pollination may occur, for the stamens far overtop the 
stigmas. 
Nectar is secreted by a narrow ring between the base of 
the receptacle and the filaments. The nectar is entirely con- 
cealed and rendered quite deep-seated by the dense circle of 
numerous stamens. 
On account of their large size and rather deeply-seated, 
concealed nectar, the flowers seem to be specially adapted to 
bumble-bees, which are in fact the principal and most efficient 
visitors, but smaller insects occur and may effect pollination, 
though by no means so readily. 
The flowers were noted in bloom from May 11 to June 22, 
The following visitors were taken May 24 and 29: — 
Hymenoptera — Apidae: (1) Apis mellifica L. 8, s., freq.; (2) Bombus 
americanorum F. 9, s., freq.; (3) B. pennsylvanicus DeG. 9, s.; (4) Cera- 
tina dupla Say 9, s.; Andrenidae: (5) Andrena sayi Rob. 9, c. p.; (6) A- 
