POLLINATION AND FERTILIZATION 149 
found a body shaped somewhat like a grain of wheat (fig. 134, 
Cand D). This body, the corpusculum, is attached at each 
side to one pollen mass of each of the two adjacent anthers 
(fig. 184, Band C). Along the corpusculum runs a slit which 
gradually narrows toward the upper end and thus acts as a 
clip, holding firmly any small object that is drawn into it. As 
the exterior of the flower is smooth and slippery, the only way 
in which an insect ean hold itself in place upon it is by insert- 
ing its claws in the slit of a corpusculum. When the insect 
corp 
Fic. 134. Flower of the milkweed (Asclepias) 
A, general view ; B, side view of flower after removal of the sepals, petals, and 
nectar-bearing organs ; C’, pollen masses with attached clip ; D, pollen masses 
with clip attached to foot of a bee; cal, calyx; co, corolla; ch, stigmatic cham- 
ber, inside of which is the stigma ; corp, corpusculum, or body to which the 
pollen masses are attached, acting as a clip; loc, locule, or pollen chamber of 
anther; po, pollen mass. All somewhat enlarged. A and C, after Prantl; B, 
after Herman Miiller ; D, after Kerner 
attempts to fly away, it drags the corpusculum and attached 
pollen masses with it, suspended by one or more claws 
(fig. 184, D), or sometimes it is held fast and dies. Hairy 
insects, like bumblebees, often carry away many pollen masses 
on the hairs of the under surface of the body (fig. 135). If 
the insect escapes from the flower and visits another, when 
it thrusts its foot through a corpusculum slit of the second 
flower the pollen masses already attached to the foot become 
torn away. The pollen masses thus detached are left in con- 
tact with the stigma of the second flower, and in this way most 
effectively secure cross-pollination. 
