18 
BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 5, NO. 1. 
large-flowered and sweet-scented T. grandiflorum with a fair sup- 
ply of nectar does not make an exception in this respect, not even 
in localities where the flowers appear in such number as to make 
them conspicuous to the human eye from a considerable distance. 
While discussing the variation in color of the flowers of T. erectum 
Robertson (3) expresses the opinion that the greenish variety is 
more or less degraded, and he states that "the flower seems to be 
losing its hold on insects and to form a transition between the 
other entomophilous species of Trill iuin and the still more 
degraded?", sessile and recurvatinn." Judging from the observa- 
tions made in our region as elsewhere it might appear as if our 
white species of TriUiitrn were altogether either repulsive or at 
least poorly attractive to insects, possibly on account of some 
peculiarity of odor. At any rate they do not seem to depend to 
any extent on cross-pollination, and are all well prepared to insure 
spontaneous self-pollination. 
In Vagnera racemosa and Unifoliiim Canadense, the two other 
species of pollen-flowers the absence of the higher bees (Apidae) 
among the visitors is noticeable. Pollen-collecting short-tongued 
bees (Andrenidse) and pollen-eating flies are the principal pollen- 
distributors, these insects furnishing about 68 per cent of the 
entire number of visitors of both fl.owers considered together. 
FLOWKRS W^ITII KXPOSED NECTAR. 
We have here, as usually in flowers of a simple structure and 
with exposed nectar a rather varied gathering of insects with a 
strong preponderance of short-tongued bees and flies, 72 per cent, 
of the totality of the visitors of the three species belonging to 
these two groups of insects. 
ElvOWERS WITH CONCEALED NECTAR. 
The two species of Trillium have been considered above 
together with the species of this genus among the pollen-flowers. 
In our three species of Allium we are dealing with three flowers 
difl^ering in structure, and accordingly attracting a somewhat dif- 
ferent set of visitors. A. Canadense the earliest among them rep- 
resents the lowest type in which the nectar is not deeply concealed, 
3. Chas, Eobertson. FloAvers and insects. XVI. Bet. Gaz. XXI. 
p. 272 (1896). 
