86 



THE ALGAE 



motion. The harder the floor tiie more regular is the shape of the 

 balls, but even so the ball structure would also appear to be in- 

 herent in the alga because ^balls' have been kept in a laboratory for 

 eight years without losing their shape. The following types of 



■jUriKWV!*,,^ 



Fig. 46 Cladophora. A, ball of Aegagropila holsatica cut through 

 and the dirt removed ( xf). B, same before cutting ( x|). C, C. 

 glomerata, commencement of septum formation. D, C. glomerata, 

 second stage in septum formation. E, C. glomerata, septum 

 almost complete. F, diagram illustrating evection. G, H, types of 

 branching. I, C. glomerata, structure of wall at a septum. J, 

 Spongomorpha coalita with hook branches. K, C. callicoma, struc- 

 ture of chloroplast with nuclei and pyrenoids. L, Ae. Sauteri, 

 zoospores in zoosporangium. M, Ae. Sauteri, zoospores. (A, B, 

 after Acton; C-K, after Fritsch; L, M, after Nishimura and 



Kanno.) 



branches have been recognized in the Aegagropila forms: (a) 

 rhizoids ; (b) cirrhoids, both these and the rhizoids being neutral or 

 non-reproductive branches; (c) stolons or vegetative reproductive 

 branches. Many of the species of Cladophora are perennial. In 

 some of the fresh-water species certain cells may become swollen 



