KEY TO THE CLASSES AND THE GENERA OF THE 

 FRESH WATER AI.GJE. 



CLASSES OF THE ALG^. 



§ Rosy red, blood-red, reddish-brown, purple or blackish; many- 

 celled . . . . . CLASS I. 



§ Chlorophyll-green, sometimes becoming crimson, purplish, flesh- 

 color or yellow-brown; 1,2 or many celled; often nucleated, 



CLASS II. 



§ Never chlorophyll-green; colorless or variously colored; i or many 

 celled; in jelly when out of the water . . . . class iii. 



KEY TO THE GENERA OF THE ALG^. 



CLASS I. 

 ^ Olive, brown or grey, black with age; filamentous, often hollow, 



bristle-like, rigid (A). ' 

 Tf Violet, violet-purple or bluish-green; filaments articulate, branched 



or not (E). 

 T[ Purple; tufts loose; filaments i in. long, not branched (D). 

 T[ Purplish, smooth, forming a firmly attached coating to stones, 



Hildebrantia, 7 

 *{ Brownish red, Vermillion, or greenish with red centre; cells 4-8, 

 free or in a short lived cluster Chlamydococcus, 38 



*{ Blood red, cells large, tegument thick, lamellose, stem ringed, 



Urococcus, 66 

 A. Filaments nodose, tufted; fertile filaments hollow, with internal 

 axillary thread; in rapid water (B). 

 ■A. Filaments transversely banded or annularly constricted; with in- 

 ternal central axis (C). 



