THE CREAT i;EOUPS OF ALG^-E 



261 



fore, t«o sorts of asexual spores are produced : (1) the 

 fef/'dxpore.^, developed in ordinary sporan,2:ia ; and (2) the 

 nirpi)s2)ores, developed in the cystocarj), which has been 

 produced as the result of fertilization. 



OTHER CIILOROPIITLL-COJS'TAIN'INfi TIIALLOPIIYTES 



1?5. Diatoms. — These are i:)eculiar one-celled forms, which 

 occur in very great abundance in fresh and salt waters. 



llllli 



Fia.'230. A prniip of rtiatnms : r and ^^ top and side views of the same form; f^, colony 

 of stalked forms iittaclief! to an alga: /and r/, top and side views of the form shovn 

 at e\ h, a colony; i. a colony, the top and side view sho^vn at k. — After Kerner. 



They are either free-swimming or attached by gelatinous 

 stalks ; solitar}', or connected in bands or chains, or im- 

 bedded in gelatinous tubes or masses. In form they are 

 rod-shaped, boat-shaped, ellijjtical, wedge-shaped, straight 

 or carved (Fig. 230). 



