Myxophyceae 163 



ter, 7-10 mic. in length, often oval; wall of gonidium smooth, 

 colorless N. foliaceum 



2 Colonies expanded, irregular or orbicular, very thin, small, mem- 



branaceous, pellucid, blue-green; trichomes 4 mic. in diameter 



N. punctatum 



3 Colonies at first spherical, afterwards becoming flattened and finally- 



spreading out into irregular, membranaceous sheets; surrounded by 

 a firm outer layer; trichomes 4-5.6 mic. in diameter 



N. commune 



4 Colonies free, spherical, becoming irregularly plicate-tuberculate, 



thick, solid, surrounded by a firm outer layer; trichomes 4-5 mic. in 

 diameter; gonidia S mic. in diameter, 7 mic. in length, oval; wall 

 of gonidium thick, smooth, becoming brownish 



N. sphaericum 



5 Colonies spherical, finally becoming flattened, membranaceous; trich- 



omes 2.5-3 rnic. in diameter N. minutum 



6 Plants living in hot water; colonies indefinitely expanded, laciniate; 



filaments 2 mic. (?) in diameter N. calidarium 



7 Colonies somewhat spherical, small, very hard, sometimes soft, with 



surface often corrugated; trichomes 6.5-8.2 mic. in diameter 



N. austinii 



VII Plants living on soil or in fresh water; colonies spherical, surrounded 



by a firm outer layer. 



1 Plants living on soil 



(i) Colonies small; trichomes 8-9 mic. in diameter; gonidia some- 

 what spherical, two or three times larger than the cells; wall 

 of gonidium thin, very smooth N. macrosporum 



(2) Colonies spherical or oblong, rarely beyond i cm. in diameter, 



somewhat pellucid; trichomes 5-8 mic. in diameter; gonidia 6-7 

 mic. in diameter, 9-15 mic. in length, oval N. microscopicum 



(3) Colonies small or of medium size, spherical; trichomes 4-7 mic. 



in diameter; gonidia 6-7 mic. in diameter, exactly spherical; 

 wall of gonidium somewhat thick, rough N. sphaeroides 



2 Plants living in fresh water 



(i) Colonies irregularly somewhat orbicular, gregarious and some- 

 times aggregated; trichomes 5 mic. in diameter 



N. depressum 



(2) Colonies spherical, usually aggregated in grape-like clusters; trich- 



omes 3.5-4 mic. in diameter N. glomeratum 



(3) Colonies gregarious, pellucid, sky blue or blue-green; trichomes 



5-7 mic. in diameter; cells barrel-shaped N. caeruleum 



(4) Colonies spherical, surrounded by a leathery outer layer; trich- 



omes 4-6 mic. in diameter N. pruniforme 



VIII Plants living in fresh water, attached; colonies somewhat spherical, 



bullate, rarely disc-shaped, surrounded by a firm outer layer; trich- 

 omes slender. 



