HOW TO KNOW THE FRESH-WATER ALGAE 



42a Aquatic; cells without individual sheaths definitely arranged in 

 4's (or sometimes in 2's) mostly at the periphery of the common 

 mucilage; under favorable optical conditions often showing long, 

 fine, hair-like extensions (pseudocilia or false flagella). Fig. 35. 

 TETRASPORA 



Fig. 35a. Tetiaspoia cylindiica (Wahl.) C. A. 

 Agardh, habit of colony; b, Tetraspoia gela- 

 tinosa (Vauch.) Desvaux, habit of colony; c, 

 arrangement of Tetraspora cells; d, single cell 

 showing cup-shaped chloroplast. 



Early in the spring or throughout the summer 

 in cold running water gelatinous, balloon-like or 

 intestiniform strands of Tetraspora may be found 

 attached to stones or to gravel, sometimes build- 

 ing masses 2 or 3 feet in length. Most of the 

 dozen or so recognizable species are macrosco- 

 pic but a few appear as microscopic, floating 

 thalli. When the colonies are young and if care 

 is used in obtaining ideal optical conditions, the 

 long fine (often shadowy) pseudocilia are dis- 

 cernible. 



Figure 35 



42b Terrestrial (usually); cells sometimes with indistinct sheaths, not 



definitely arranged in 4's; without pseudocilia. Fig. 36 



PALMELLA 



} Fig. 36. Palmella miniata Liebl. a, 

 habit of colony; b, portion of col- 

 ony showing arrangement of cells 

 and individual cellular sheaths. 



This plant forms lumpy gelatin- 

 Figure 36 ous masses, 2-8 or more millimeters 



in diameter on damp soil or on rocks, 

 especially about water falls. The cells of P. miniata are often red 

 with the pigment haematochrome, whereas P. mucosa (without indi- 

 vidual cellular sheaths of mucilage) is always green. 



38 



