154 Minnesota Algae 



within sandstone rock, as far at least as 10-15 mm. from surface; sheaths 

 cylindrical, rough, usually colorless and not lamellose, but sometimes 

 brownish and lamellose; trichomes 3.5-4.8 mic. in diameter, not constricted 

 at the joints, one to many in a sheath; apical cell truncate conical; cells 

 5-8 mic. in length; transverse walls usually invisible. 



Minnesota. In bare and dry sandstone cliffs. Soldiers' Home, Minne- 

 haha Falls. September 1896. (Hall). 



Genus DASYGLOEA Thwaites. Eng. Bot. pi. 2941. 1848. 



Sheaths very wide, colorless or yellowish brown; trichomes very few 

 within the sheath, very loosely aggregated; apex of trichome straight, not 

 capitate; cells often longer than the diameter. 



298. Dasygloea amorpha Berkeley in English Botany, pi. 2941. 1848. Go- 



mont. Monogr. Oscill. 84. pi. 13. f. 11, 12. 1893. De Toni. Syll. 



Algar. 5: 368. 1907. 



WoUe. Fresh Water Algae. III. Bull. Torr. Bot. Club. 6: 183. 1877; 



Fresh-Water Algae U. S. 304. pi. 204. f. 1-9. 1B87. (M icrocoleus 



amorpha (Thwaites) Wolle). 



Plate VI. fig. 26. 



Plant mass amorphous, gelatinous; filaments twisted, entangled, divid- 

 ed into fringes at the apex; sheaths transparent throughout, or dull yel- 

 low within, very irregular in outline, mucous, sometimes somewhat lamel- 

 lose; trichomes 4-6 mic. in diameter, constricted at joints; apex of trichome 

 sometimes very gradually tapered; apical cell truncate conical; cells 4-13 

 mic. in length; cell contents coarsely granular. 



Pennsylvania. Forming a thin olive or dark blue-green membrane, 

 skin-like, on trickling rocks in mountain ravine. Glen Onoko. (Wolle). 



Genus MICROCOLEUS Desmazieres. 

 Cat. des Plantes omises dans la Botanographie Belgique. 7. 1823. 



Plants living on soil, in fresh water or sometimes in salt water; fila- 

 ments pimple or vaguely branched, creeping on the ground, sometimes 

 growing among other algae; sheaths colorless, more or less regularly 

 cylindrical, not lamellose, in many species finally diffluent; trichomes 

 many within the sheath in well developed filaments, closely crowded, 

 often twisted into rope-like bundles; apex of trichome straight, tapering; 

 apical cell acute, rarely obtuse conical, in one species capitate. 



I Plants living in salt water; apical cell not capitate, pointed. 



1 Trichomes 1.5-2 mic. in diameter, constricted at joints 



M. tenerrimus 



2 Trichomes 2.5-6 mic. in diameter, constricted at joints 



M. chthonoplastes 



II Plants living on soil; apical cell capitate. M. vaginatus 



