272 



A TEXTBOOK OF BOTANY 



[Ch. VI, 2 



Next inside the corolla conies the whorl of stamens. 

 Each consists of a slender cylindrical stalk, the filament, 

 bearing at its tip an enlarged rounded yellow anther. A 

 lens will show that this anther opens by longitudinal slits, 

 allowing the escape of a yellow powdei- (each grain of which 

 is a cell), callefl pollen. Pollen contains the male sex cells 

 of the ])lant, which later fertilize the female sex cells in the 

 ovules, as presently to be noted. The filaments are some- 

 times short, even to disappearance, but again are elongated 

 almost to thread-like, as in Night-blooming Cereus. Often- 



cst cylindrical, they are 

 sometimes flat and even 

 petal-like, as in Water 

 lilies, where it is difficult 

 to say whether the fila- 

 ments are petal-like or 

 petals bear the anthers. 

 The anthers, typically 

 rounded, are sometimes 

 greatly elongated, or 

 forked, or otherwise re- 

 markably shaped, while 

 thc}^ open in very diverse ways. Usualh' forming a direct exten- 

 sion of the filament, they are sometimes balanced on the point 

 thereof, as familiar in the larger Lilies. C'onnnonly quite 

 separate from one another (polyadelphous), thej' some- 

 times form one piece at their bases (monadelphous), as 

 in some of the Pulse family, and Abutilon. While typically 

 they stand directlj' on the receptacle, they are often on 

 corolla or calyx. Their existence is fleeting like that of the 

 corolla, with which they conuuonly fall. While often 

 numerous, as in l^eouA', Buttercup, antl Rose, they are 

 connnonly limited in number, Ijeing typically the same num- 

 ber, or double the niniibei', of the petals, an<l therefore 

 oftenest five or ten, or else less fr(H|uently three or six, or four 

 or eight, though other numbers occur with lesser frequency. 



Fig. 185. — Generalized forms of 

 ovules, showing the principal arrange- 

 ments on the stallcs ; magnified. 



Left, upright, orthotropous, form like 

 Fig. 184 ; middle, inverted on elongated 

 attached stallv (raphe), anairopous ; right, 

 curved over to inversion, cam pyloiro pous . 

 (Reduced fr(jm Strasburger,) 



