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. 339). 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 (Pig. 239, 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 

 apex of the carpogonium, 



itlEi an antheridium. o,"and a carpogonium, " wliprp j-Vip ppII wall in an 

 Burrounded bs th,- spirally twisted envelop. w^ere tnC CCli-waU IS ap- 

 ing cells ; c. crown of five cells at apex; p, parently absent ;" aS a re- 

 sterile lateral leaflets ; /J'^ large lateral leaf- 

 let near the fruit ; ,8", bracteoles springing 



Fig. 828.— Eeprodnctive organs of Ohara 

 fraatlis. A, a. central portion of a leaf, J, 

 itn a 



suit of this union, 



re- 

 the 



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



gans, B, a young antheridium, a, and ^ ,-..■.-.-,-. , 



young carpogonium, sk: w. nodal cell of thicker Wallcd, hard, and 



l^af ;«, inleiinediale cell between M) and the ■■ , i j j? 



basal node cell of the antheridium ; I, cavity OarK - COlored, lOrming a 



of the internode of the leaf ; 6r, cortical cells j j • x- 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 germination. 



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 



