Dogbane and Milkweed 311 
flower, upside down. Inside this firkin are two 
green pistils, which may become two green pods, 
Half the pollen of each anther is collected into a 
nine-pin-shaped mass, which is fastened to a sim- 
ilar mass formed by half the pollen of the next 
anther. Thus two connected pollen-masses belong 
to two separate stamens. 
They are united by a tiny black disk, which is 
seen, on closer examination to be thin, hard, and 
horny (Fig. 87, d). ‘‘Its sides are bent forward 
for its whole length,’’ says Miller, ‘‘so that their 
edges lie close together, and in the middle of its 
lower border is a wedge-shaped notch.’’ The disk 
is set just above an opening between the stamens 
which runs ‘‘ clear through’’ to the pistils inside 
the firkin. This opening is a mere slit at its 
widest part, but it is distinctly narrower at its 
upper end. The fly or bee stands on the outside 
of the firkin, and slips and slides on the smooth 
surface till one of her feet enters the lower and 
wider end of one of the slits. 
The winged captive draws her leg upward in the 
effort to escape, and her foot catches in the notch 
on the lower side of the little black disk. Then, 
determined to be free, she pulls out, if she is 
strong enough, the whole affair, disk and attached 
