golden-brown in color, tapering toward the apex, which is capitate; 

 cells 6-8;a in diameter, S-d/x long. 



In small pools on rock cliffs. Pictured Rocks, Michigan. 



MICROCOLEUS Desmazieres 1823, p. 7 

 Plant mass consisting of many parallel trichomes inclosed by a 

 wide, gelatinous, homogeneous and sticky sheath; trichomes with 

 basal-distal differentiation, tapering anteriorly to conical or capitate 

 apices, closely entwined, sliding upon one another in and out of 

 the sheath; cells quadrate or elongate-cylindric; contents granular 

 but without pseudovacuoles; cross walls sometimes granular; plants 

 mostly on moist soil, sometimes submerged on old wood in a gela- 

 tinous mixture of miscellaneous blue-green algae. 



This genus should be compared with Schizothrix, which has firm 

 colored sheaths, often forms erect tufts or fascicles of filaments, and 

 is seldom aquatic. 



Key to the Species 

 1. Apical cell capitate M. vaginatus 



1. Apical cell not capitate 2 



2. Trichomes 4-5^ in diameter, constricted 



at the cross walls; aquatic M. lacustris 



2. Trichomes 5-7/li in diameter, not constricted at the cross walls; 



plants usually on moist soil M. paludosus 



Microcoleus lacustris ( Rab. ) Farlow in Far low, Anderson, & 

 Eaton 1877, Algae Amer. Bor. Exsic, No. 227 

 PI. 113, Fig. 6 

 Aquatic; forming dark blue-green patches on submerged wood 

 or on bottom. Sheaths colorless, confluent with the sheaths of other 

 filaments, thin and evanescent at the ends; not stained by chlor-zinc- 

 iodide reagent. Trichomes with bluntly tapering apical cells, not 

 capitate; 4-5/i, in diameter. Cells distinctly cylindrical, constricted 

 at the cross walls; 8-14/x long; contents finely granular, blue-green. 

 Among other filamentous blue-green algae in tychoplankton and 

 adhering to submerged substrates. Mich., Wis. 



Microcoleus paludosus ( Kuetz. ) Gomont 1892, p. 358 



PI. 113, Fig. 5 

 Filaments either solitary among other algae or entangled to form 

 dark green, thready masses; sheaths either closed and pointed ( some- 

 times forked) or open; sheaths sticky but not especially confluent, 

 not colored by chlor-zinc-iodide reagent; trichomes compactly en- 

 twined, tapering to blunt, conical apices, which are not capitate; 



[505] 



