SEXUAL REPRODUCTION. 



281 



of the ganietophyte and the others the spermary (fig. 316). 



In angiosperms the vegetative jiart seems to have vanished 



and the two cells whicli. aie fjrnit 1 t istitute the sj ennary-, 



the smaller representing 



the sperm cells and the 



larger the wall cells (fi^ 



317 ; compare fig. 315) 



Sometimes, indeed, the 



smaller cell is onl)- repre 



sented by a nucleus, nj 



partition wall being pres 



ent. Thus, the spermar\ 



in allseed plants has almo t 



become a simj.ile one agam 



by reduction from the com 



pound spermary of their 



ancestors. By this extreme ri ^13—4 pan of a leaf fchara, bear- 



, . ing sexual organs. b, leaf; ^, undeveloped 



reduction Ol the male game- ■■iMflets"; P', leaflet; 3", leaflets of the 

 . . branch, sc \ tlie dark oval body is the o\'ary 



tOph)te, that fS, to a sex containing the fertilized egg; i, Ave cortical 



cells which ha\'e gro\\'n spirally around the 



organ alone, almost all trace ovary proper and become adherent to it; 



they terminate in c, the five crown cells, be- 



Of resemblance to a plant tween which the sperm makes its way to the 



egg; a, the spermary, showing four of the 

 y toothed plates of which its wall is composed, 

 and the center of each to which on the inside 

 the handle cell is attached. Rfagnified 33 

 diam. A', longitudinal section through young 

 " node " of a " leaf " of Chara, showing origin 

 and young stage ot sexual organs. / and w 

 stand in the corners ot the adjacent internodal 

 cells ; between them is the thin nodal cell 

 from which arise t and the sexual organs sk 

 . and a ; br , cortical cells co^■ering /, i". sk 



tremely small and simple is the young ovary not yet overgrown by the 

 . cortical cells at its sides, n. the spermaiT, 



even when mature, is the shows four wall cells outside, from which 



their handle cells have just been di\'ided ; 



exact homologue of the all too young to show relative sizes or shapes. 



Magnified 240 diam. — After Sachs, 



larger male [jlant jjroduced 



by the spores of the mosses, ferns, horsetails and selaginellas. 



386. Pollen tube. — The maturity of the male gametophyte 



is reached only after the microspore has been caught by the 



moist surface (fluid in the micropyle or on the stigma) pro- 



has been lost, and it is diffi- 

 cult to think of the pollen- 

 grain (microspore) as pro- 

 ducing a real plant. This 

 male plant, though ex- 



