436 STRUCTURE AND LIFE HISTORIES 
Each stamen consists of a slender stalk, the filament, 
bearing at its tip two microsporangia (pollen-sacs), 
united to form the anther. In the pollen-sacs are numer- 
ous microspores, which finally develop into pollen- 
grains. 
FIG. 323. Wood lily (Lilium philadelphicum). 
A central organ, the pistil, composed of three mega- 
sporophylls (carpels} united, and enclosing the mega- 
sporangia (ovules}. All the pistils taken together (one or 
more) constitute the gynoecium. 
The pis.til consists of three distinct regions as follows: 
(a) The enlarged basal part, enclosing the ovules, 
and hence called the ovary. 
(b) A slender upward prolongation of the ovary, 
