No. IO.] FRESH-WATER ALCE. 45 



5. Cells with thick lamellose coats, in a series inside a 



lamellose sheath cylindrocapsace^e 



Cells without lamellose coat ulotrichace^: 



FAMILY I. TRENTEPOHLIACE.E. 



Thallus filamentous and branched, filaments erect or creep- 

 ing-, growing on the ground or on tree trunks. The cell walls 

 are firm and lamellose. The cells are uninucleate, and possess 

 one or many parietal chloroplasts with or without pyrenoids. 

 The color of the plants is usually brown or reddish. Zoogo- 

 nidia are developed only in cells especially set apart, either on 

 the ends of the branches or intercalated. These motile spores 

 sometimes conjugate. Spores are sometimes produced which 

 rest for a period before germinating, called resting spores or 

 hypnospores. 



Key to Genera. 



Terrestrial or arboreal ; chloroplasts several 



Trentepohlia* 

 Aquatic ; cells that produce zoogonidia are terminal 



Gongrosira 

 Aquatic ; cells that produce zoogonidia not terminal 



Leptosira 



Description of Genera. 



Trentepohlia Mart. (Chroolepus Ag.). Filaments 

 irregularly branched, often so dense that the branches and 

 stem cannot be easily distinguished ; primary branches and 

 stem of same thickness. Cell contents reddish brown, golden- 

 yellow, or olive-colored. About 32 red-brown or golden-yellow 

 zoospores in a cell which is set apart especially for the purpose, 

 usually on the end, sometimes on the side of the filament. 

 [T. aurea (L.) Mart.; T. Iolithus (L.) Wittr.] 

 Gongrosira Kiitz. (inclus. Pilinia Kiitz., in part). The 

 plant is attached by a mass of cells, formed by a confluence 

 of creeping branches. From this mass, which may be of one 

 or many layers of cells, numerous erect branched filaments 

 arise. The whole is frequently encrusted with lime. The cell 

 walls are thick and lamellose, and the chloroplast is parietal 

 with one or many pyrenoids. Zoogonidia are found in flask- 



