HOW TO KNOW THE FRESH-WATER ALGAE 



test must be used to differentiate the two genera. Characiopsis often 

 shows one to several spherical droplets of oil (?) or other food reserve 

 in the cytoplasm which are not present in Characium. 



310a (307) Cells with a vase-like, pitcher-shaped or globose lorica (en- 

 velope) with a neck and a terminal opening. Fig. 218 



STIPITOCOCCUS 



Fig. 218. a, Stipitococcus vasitor- 

 mis Tiffany; b, S. urceolatus 

 West & West. 



There are 3 or 4 species of this 

 genus of rather uncommon occur- 

 rence, although in particular habi- 

 tats the various species are rela- 

 tively abundant and filamentous 

 algae may be densely overgrown 

 with the epiphytes. S. urceolatus 

 West & West is perhaps more fre- 

 quently seen than others and is easily identified because of its distinc- 

 tive, pitcher-shaped lorica. 



310b Cells without a lorica 311 



Figure 218 



311a Cells cylindrical, straight or curved, sometimes with a spine at 

 one or both ends. Fig. 219 OPHIOCYT1UM 



Fig. 219. a, e, Ophiocytium parvulum (Perty) 

 Braun; b, O. gracilipes (Braun) Rab.; c, O. 

 cochieare (Eichw.) Braun; d, O. desertum 

 var. minor Presc. 



The factors which determine the distribution 



of this genus are unknown, but there seems 



to be good evidence that water chemistry 



determines the presence of these species, of 



Cx — O^ ( which there are several reported for the 



United States. Where one species is found, 

 ^ \\ several others also occur as well as many 



other genera of the Xanthophyceae, a class 

 of the Chrysophyta to which this genus be- 

 longs. Species are differentiated by presence 

 or absence of polar spines, and whether free- 

 floating or stalked and epiphytic. They usually occur intermingled 

 with miscellaneous algae from the shallow water of swamps and bogs, 

 occasionally appear in the euplankton of lakes: Most species are soli- 

 tary but attached forms may be incidentally colonial. 



Figure 219 



134 



