VEGE TA TIVE REP ROD UCTIOM. 



M7 



347. Sporangia.— The anther bears from 1-12 micro- 

 sporangia upon its surface, or wholly or partly sunk in its 



Fig. 262.— Transverse section of the anther of thorn-apple (Datura Stramonium). 

 c, connective, with a small stele embedded in parenchyma ; a, />, a, /, the four spo- 

 rangia, arranged in pairs showing pollen grains. When the sporangia break, the walls 

 rupture at the groove between a and /. Magnified about 25 diam. —After Frank. 



tissues. In most anthers the sporangia are either 2 or 4 



(fig. 262). When there are four they are often paired, and 



each pair may become confluent by 



the absorption of the portion of the 



anther tissue between them (fig. 263). 



This occurs about the same time that 



the outer wall bursts in order to set 



free the spores. Such anthers, at the 



time of opening, are apparently two- 



chambered. In those which contain 



only two sporangia, the two may open Fig. 263. -Trans verse section of 



. . bursted anther of a lily (Bu- 



independently, or they may become tomus umbeiiatus). Sporangia 



n , , have ruptured at z, so th.it the 



confluent, so that at maturity they two pairs have each formed a 



single cai itv. The coi 

 may seem to constitute a single is relatively small; in the centei 



a single stele. Magnified about 

 chamber. 2odiam. mm Sachs 



348. Dehiscence. — The opening of the 1 hambers occurs in 



one of three ways : by pores, by slits, or by valves. (1) A small 



area of the outer wall is absorbed or breaks away so that the 



