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 Muller, "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 



