134 



ELEMENTARY STUDIES IN BOTANY 



three of the petals entering into the structure of the upper 

 lip, and the other two petals forming the lower lip (Fig. 103, 

 C, D, E). Such a corolla is naturally called bilabiate (" two- 

 lipped "), and a large family of the Sympetalae is called the 

 Labiatce (" lipped ") because its flowers have this two-lipped 

 structure. These are simply conspicuous 

 illustrations of irregular corollas. 



82. The stamen. It was among the 

 Angiosperms that the name stamen was 

 given long ago to the sporophyll that 

 bears microsporangia, and since it was 

 recognized to be necessary to seed-forma- 

 tion, it was thought to be the male organ, 

 and the pollen grains (microspores) it 

 produced were thought to be male cells. 



FlG of\^e^mrstSr Jt is ey ident tnat sporophylls and mi- 

 showing filament and crospores belong to the sporophyte, a 



anther, the latter ap- , . ,. . , , 



sexless individual, so that the stamen 

 cannot be a male organ. The mistake 



which the sac splits 

 to discharge the pol- 

 len. After SCHIM- 

 PEB. 



chiefly as two 

 pollen sacs ; the ver- 

 tical line shown in 



the left pollen sac of wa s natural, because the minute gameto- 



the left stamen in- 



dicates the line along phytes had not been discovered. 



The stamens of Angiosperms vary ex- 

 tremely in appearance, but in most cases 

 two distinct regions can be recognized 

 (Fig. 104). There is a stalk-like region, which is long or 

 short, slender or broad, called the filament, and a terminal 

 region that bears the microsporangia, called the anther. 

 The filament puts the anther in a favorable position for dis- 

 charging its pollen grains, which are to be carried away by 

 the wind or by insects or by some other agency. 



The anther consists of the top of the sporophyll and usually 

 four microsporangia, two on each side (Fig. 105). As the 

 microsporangia grow, the two on each side usually run to- 

 gether and become one cavity (Fig. 106), so that in the mature 

 anther there are usually two sacs (Fig. 104) containing pollen 



