HOW TO KNOW THE FRESH-WATER ALGAE 



371a Cells joined together by long, narrow protoplasmic extensions, 

 arranged in a linear series. Fig. 266 CHRYS1DIASTRUM 



Fig. 266. Chrysidiastrum catenation Lau- 

 ter. (Redrawn from Smith). 



Although this organism may occur 



singly it is- frequently seen adjoined 



in loose colonies by the interconnecting 



pseudopodia. There is 1, plate-like or 



Figure 266 disc-shaped chromatophore. 



371b Cells not joined as above 



372 



372a Pseudopodia numerous, radiating needles; colony formation most- 

 ly temporary and incidental. See Fig. 249 RH1ZOCHRYSIS 



372b Pseudopodia short protoplasmic extensions which join individuals 

 to form temporary colonies. See Fig. 250 CHRYSAMOEBA 



373a (370) Colony consisting of vase-shaped envelopes, 1 or 2 such 

 envelopes arising from the mouth of one below to form forked 

 series (organisms actually motile by flagella, but often appear- 

 ing quiescent with flagella completely invisible in microscope 

 mounts). See Fig. 243 DINOBRYON 



373b Individuals not cone-shaped; colony formed otherwise 374 



374a Thallus a sparsely branched gelatinous cylinder or a mucilaginous 

 network, with cells arranged in 1 to several irregular linear series. 

 Fig. 267 PHAEOSPHAERA 



Fig. 267. Phaeosphaera perforata Whitford. a, 

 small portion of perforate colony; b, cells 

 showing chromatophores. 



The golden brown cells of this species occur 

 in gelatinous masses of irregular shape and of 

 macroscopic size. The thallus may be a stringy 

 mass of mucilage occurring in skeins or mesh- 

 works. Unlike Tetraspora (Fig. 35) with which 

 it might be mistaken, the cells are not arranged 

 in groups of 4 but occur in irregular series 

 throughout the gelatinous strands. 



Figure 267 



374b Thallus not a branched gelatinous strand or network 375 



156 



