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 

 a ? ex of the carpogonium, 

 rl " where the cell - wa11 is a P- 



ing cells ; c, crown of five cells at a|.ex ; /3, pareiltly absent ;" as a re- 

 sterile lateral leaflets ; 8' large lateral leaf- , , . , , , , 

 let near the fruit ; '', bracteoles springing llt of this Union, the 

 fiom the basal node of the reproductive or- enveloping Cells become 

 gans. B, a young amheridmm, a, and .,._* njv j j 

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



dark -colored, forming a 

 ! Sx'S'SS dense and resisting coating 

 Sach8 - 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 



