332 



BOTANY. 



which are at first filled with granular protoplasm ; after- 

 ward each cell develops a single spirally coiled spermato- 

 zoid. When the antheridium is mature i.e., when the 

 spermatozoids are fully formed the shields separate from 

 each other, and thus expose the filaments (Fig. 229). The 

 spermatozoids escape by the rupture of the walls of the fila- 

 ment cells ; each consists of a slender spiral thread of proto- 

 plasm, thicker at one end than the other, and provided at 



the more attenuated ex- 

 tremity with two very del- 

 icate and greatly elongated 

 cilia (Fig. 229, d). By 

 means of these cilia the 

 spermatozoids movf 

 through the water with a 

 spiral rotary motion. 



432. Fertilization takes 

 place by the entrance of 

 spermatozoids through the 

 orifice between the diverg- 

 ing cells of the crown ; they 

 come in contact with the 



Fig. 228. Reproductive organs of Chara ar , pv o f f|, p pornno-nniiim 

 fraqilis. A. a central portion of a k-af, b, a P ex c tne CaipOgOl UHl, 

 with an antheridium. a, and a carpogoninm, tt wliprp flip ppll-wall is ftrt- 

 *, surrounded bv tin- spirally twisted envelop- 

 ing cells ; c, crown of five cells at aj.ex; ft parently absent ;" as a re- 

 sterile lateral leaflets ; /3', large lateral leaf- -, , X ,-, , 

 let near the fruit ; /3", bracteoles spring ng sult ol tnls Union, tne 

 from the basal node of the reproductive or- enveloping Cells beCOme- 

 gans. , a young antheridium, a, and n . 



youni: rnrpogonium. sk; w. nodal cell of thicker Walled, hard, and 



Iaf ; ii. intermediate cell between w and the j , i j j> 



basal node cell cf the antheridium ; I. caviiy dark - Colored, lOrmmg a 



of the intf mode of the leaf ; br, cortical cells > j , 



of the leaf. A x about 33 ; B x 240.-After dense and resisting coating 



to the fully formed carpo- 



spore within. The seed-like sporocarp thus formed soon 

 separates itself from the parent plant and falls to the bot- 

 tom of the water, where it remains until the advent of favor- 

 able conditions for germinati.on. 



433. In germination the sporocarp gives rise first to a 

 simple structure consisting of a single row of cells (the pro- 

 embryo), and from this the more complex sexual plant is 

 developed by the growth of a lateral bud-cell. The sexual 



