FIG. 125. 



THE STAMENS. 

 FIG. 126. FIG. 127. Fro. 128. 



79 



FIG. 129. 



Dilated. 



Petaloid. 



Bi-dentate. 



Bi-dentate. 



EXERCISE XXIV. 

 Structure and Forms of Pollen. 



The pollen-grain is generally composed of two 

 membranes, or coats, filled with a thick liquid sub- 

 stance containing minute grains, which is its essential 

 portion. The outer coat is frequently marked with 

 bands, lines, and grooves, or covered with bristling 

 points (Fig. 131). The inner coat is very thin, and 

 swells when wetted. If you moisten pollen-grains ? 

 you may often see, with a microscope, the expanded 

 inner coat protruding through openings in the outer 

 coat (Fig. 131). 



EXTTNE. The outer coat of a pollen-grain, usually 

 with openings, or very thin in certain places (Figs. 

 131, 132, and 133). 



INTINE. The inner coat of a pollen -grain, very 



