34 NATURE SKETCHES IN TEMPERATE AMERICA 



ground, and while viewing these sights, a Baltimore oriole snaps 

 at some selected winged morsel. Like the mulberry tree in its 

 attraction for birds, so the hnden tree, in full blossom, is a 

 delight to the senses of insect life, causing them to divide their 

 attention between it, the chestnut, and the elderberry, which 

 all blossom at the same time. Near one of the large basswood 

 trees, where a view may be gained into its upper branches, the 

 floral display alone, with its treat of perfume, is sufficient attrac- 

 tion; but, coupled with the harvest of insect visitors, one may 

 easily spend a profitable hour contemplating the wonderful 

 view, and adding something to the meaning of this great 

 activity. 



On examining the flowers of the basswood, the honey is found 

 secreted and held in the hollow sepals. "The petals and 

 sepals are overtopped by the numerous stamens which curve 

 outward so that insects can only alight on the anthers, or on 

 the stigmas and the space between them. The possibiUty of 

 self-fertilization is almost excluded by the stamens remaining 

 bent outward to the last, while the pistil occupies the axis of 

 the flower; only rarely is a flower met with in which an anther 

 has become curved inward to touch the stigma." ' 



The honey is only accessible to insects with short tongues. 

 As none of the bees visiting the basswood blossoms had pollen 

 in their baskets, Miiller concluded that these insects visited 

 the flowers for the honey and not for the pollen. There is an 

 explanation of the cause of the diverse forms of insect frequenters 

 to the basswood blossoms if we remember the observations of 

 Knuth: "First, the more specialized a flower — i.e., the more 

 complex its structural arrangements and the more deeply seated 

 its nectar — the less are its insect visitors indiscriminately 

 drawn from the entire insect fauna of a district, and the more 

 do they belong to one or several similar species adapted to 

 pollination. Secondly, the flatter and more superficial the 

 position of the nectar, the more varied are the visitors in different 

 regions, and the more are they indiscriminately drawn from 

 the entire insect fauna of the region in question." ^ 



The basswood blossoms, shown in the plate illustration, 



• Mtiller, "Fertilization of Flowers," p. 146. 

 2 "Handbook," Vol. I, 1906, p. 196. 



