192 



Introduction to Botany. 



Fig. 107. 

 Asclepias cornutl. 



Stamens (r) are joined throughout their length, and are 

 united to a thick and flat structure (t) at their apices, 

 known as the stigmatic disk, which is also united with 



the top of the two 

 pistils (w). The pistils 

 are entirely inclosed by 

 the stamens and the 

 stigmatic disk. Five 

 spreading, hollow re- 

 ceptacles (7') for the 

 nectar grow out and 

 upward from the bases 

 of the stamens. 



Each pollen sac con- 

 tains a compact mass of 

 pollen grains (w) which 

 never become separated 

 from one another, and 

 so constitute what is 

 termed a polliniiim. 

 The two contiguous pol- 

 linia of adjacent anthers 

 are united by horny 

 rods {x) which converge 

 upward and join with a 

 horny dark body (jj/) known as the corpuscidum, which 

 is hollow and has a slit along its outer face. This slit 

 is relatively broad at the bottom, and tapers toward the 

 top, thus forming a clip in which the feet of the insects 

 get caught. Between each pair of anthers there is a 

 deep recess closed by two vertical lips which stand wider 

 open at the bottom than at the top, and the recess also' 

 narrows at the top. The opening between the Hps at 



