326 



PART III. THE CLASSIFICATION OF PLANTS. 



A 



Fie. 233. Fnnaria hygromet- 

 rica (Moss). A An antheridium 

 bursting : a the ppermatozoids 

 (x 350). B Spernnatozoids 

 ( x 800) ; b in the mother-cell ; 

 c free spermatozoid of Poly- 

 trichum. 



FIG. 234. A Antheridinm of Marchantia polymorplia (Liver- 

 wort) in optical longitudinal section: p paraphyses (x 90). 

 B Spermatozoid s ( x 600) : (after Strasburger). 



The sexual organs are always multi- 

 cellular. The antheridium (Figs. 233, 

 234) is a capsule of various shape, hav- 

 ing a longer or shorter stalk ; its wall 

 consists of a single layer of cells which 

 contain chloroplastids when young ; in- 

 ternally it consists of very numerous 

 small cells, each of which, eventually 

 gives rise to a single spermatozoid. 



The spermatozoid is a cell, consisting of 

 a naked filament of protoplasm, spirally 

 twisted, thickened at the posterior end 

 where lies the nucleus, tapering at the 

 anterior end where it terminates in two 

 long cilia by means of which it swims 

 (seep. 116); the spermatozoids are set 

 free by the rupture of the antheridial 

 wall, which usually takes place at the 

 apex of the antheridium. 



The archegonium is flask-shaped and 

 shortly stalked (Figs. 235, 236) ; it con- 

 sists of a slightly dilated basal portion, 

 the venter, and of a long slender neck. 

 The axis of the archegonium, when 

 young, is occupied by a central row of 

 cells ; the basal cell of this row, lying in 

 the venter, is the 

 central cell of the 

 archegonium ; it 

 grows consider- 

 ably, and event- 

 ually divides into 

 two unequal parts, 

 an upper and 

 smaller, the ventral 

 canal- cell, and a 

 lower and larger 

 which is the female 

 reproductive cell 

 or oosphere: the 

 upper cells of the 



