202 



THE 



B 



FIG. 192. The stonewort (Chara) 



A, portion of plant showing circles of lat- 

 eral hranches at the joints (nodes) ; B, a 

 lateral branch bearing the sexual organs ; 

 C, the sexual organs; o, oogoniura, with 

 spirally wound filaments encircling the 

 egg and forming a crbwn above; a, the 

 antheridium, composed of eight flattened 

 cells (shields), inclosing the antheridial 

 filaments; D, portion of an antheridial fila- 

 ment, each cell developing a single sperm ; 

 E, two-ciliate sperms 



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 

 antheridium of the stone- 

 worts is a very puzzling 

 structure but the oogonium 

 is easily understood. The 

 jointed stems with circles 

 of lateral branches are, of 

 course, much more com- 

 plicated than the typical 





thallus, but the simple life 

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

 necessary to include the stoneworts among the thallcphytes. 



