Rivulariacese 



45 



form an expanded stratum on wet rocks and submerged stones (fig. 35). In Rioulari. the 

 filaments are disposed to form subglobosc or hemispherical, attached masses, sometimes 



Fig. 34. 



" 



)$> i 



B 



M- ffl fk ; -|iv 41. D 

 ^W%i^^M 



~"" H^> 



-^ 



and B, Stigonema miinitniii Hass. ; A, xlOO; J5, x 440. C E, St. ocellatum 

 (Dillw.) Thur. ; C, xlOO; D and A', x 400. /;, beterocyst. 



Fig. 35. J and B, Calothri.r prictina (Nag.) Tlinr. C, Dichothri.v inter rapta W. & 

 G. S. West. D, D. Orsiniana (Kiitz.) Born. & Flah. All x 420. 



gelatinous and sometimes incrusted with lime. In Gloeotrichia, which occurs largely in 

 the plankton, the gelatinous mass is usually free-floating. The genus scarcely differs from 

 Rivularia, except in the formation of large cylindrical resting-spores. In Homceothrix 

 and two other genera there are no heterocysts. 



