202 



THE ALGvE 



between the circles of lateral 

 branches. The protoplasm 

 passes in two streams in op- 

 posite directions somewhat 

 diagonally around the cell. 

 The edges of the stream 

 form a line of stationary 

 protoplasm (free from chlo- 

 roplasts), because the move- 

 ments of the currents, which 

 may be seen on either side 

 of the line, neutralize one 

 another. 



The Charales stand en- 

 tirely by themselves at the 

 end of a line of ascent whose 

 developmental history is a 

 mystery. They are very 

 far above most of the green 

 algse in the complexity of 

 the plant body and sex- 

 ual organs, which are not, 

 however, like those of the 

 liverworts and mosses. The 

 FIG. 192. The stonewort (Cham) antheridium of the stone- 

 A, portion of plant showing circles of lat- W0rts is a V61 T puzzling 

 eral branches at the joints (nodes) ; B, a structure but the OOgonium 

 lateral branch bearing the sexual organs ; --i j i mi 



C, the sexual organs! o, oogonium, with 1S easil 7 understood. The 

 spirally wound filaments encircling the jointed stems with circles 

 egg and forming a crown above; a, the P , , , , , f 



antheridium, composed of eight flattened of lateral brandies are, of 

 cells (shields), inclosing the antheridial course, much more COm- 

 filaments; I), portion of an antheridial fila- ,. -, ,, ,-. , 



ment, each cell developing a single sperm; Plated than the typical 



E, two-ciiiate sperms tliallus, but the simple life 



history, with no trace of an alternation of generations, makes it 

 necessary to include them among the thallophytes. 



B 



