ULOTRICHALES 



45 



filament and then successively in the other cells. They are liberated 

 through a hole in the side of the cell into a delicate vesicle, and the 

 subsequent bursting of this vesicle frees the swarmers, all of which 



Fig. 33. Ulothrix zonata. A, B, rhizoid formation. C, liberation of swarmers 

 into vesicle ( x 375). D, germination of aplanospores in the cell ( x 250). E, libera- 

 tion of gametes ( x 375). F, escape of zoospores ( x 375). G, akinetes of U. idio- 

 spora. H, palmelloid condition. I, schema to illustrate the different types of 

 filaments and swarmers. J, K, aplanospores ( x 400). L, zoospore formation 

 ( X 400). M, banded chloroplasts in a portion of the vegetative filament ( x 400). 

 (A, B, I, after Gross; C-F, J-M, after West; G, H, after Fritsch.) 



are positively phototactic. Three types of swarmer are to be found. 

 (a) Quadriflagellate macrozoospores, of which two, four or eight 

 are produced per cell. After a motile period these become broader 

 than they are long, attach themselves to a suitable substrate, and 



