Myxophyceae 229 



Filaments decumbent, reddish, dichotomously branched, entangled; 

 false branches spreading, abruptly bent; cells shorter than their diameter. 

 West Indies. On fallen leaves. Cuba. (Montagne). 



425. Scytonema simplex Wood. Contr. Hist. Fresh-Water Algae North 



America. 57. 1872. Wolle. Fresh-Water Algae U. S. 259. 1887. (S. 

 simplice Wood !!). De Toni. Syll. Algar. 5: 536. 1907. 



Plant mass moderately thick, somewhat cushion-like, blackish green; 

 filaments 10-15 ™c- in diameter, very long, fiexuously curved, sparingly 

 branched or without branches; false branches in pairs or single, usually 

 elongate; sheaths thick, transparent, often colorless, sometimes pale yel- 

 lowish brown, mostly open and truncate at apex; trichomes 3-6 mic! in 

 diameter; cells equal to seven times as long as broad (?), often separated, 

 apical cells very short; heterocysts cylindrical, scattered, two to five times 

 longer than their diameter; cell contents sparsely granular, pale greenish. 



South Carolina. Adhering to the wet sides of a wooden gutter leading 

 water from a spring. Aiken. September 1869. (Ravenel). 



Genus TOLYPOTHRIX Kuetzing. Phyc. Gen. 227. 1843. 



Filaments branched; false branches usually arising in the immediate 

 region of the heterocysts, rarely between two heterocysts, single; sheaths 

 somewhat thin, flexible, more or less fragile; gonidia spherical, oval or 

 elliptical, often many in a series; wall of gonidium smooth, thin. 



I Sheaths thin. 



1 Plants living in water 



(i) Filaments 8-10 mic. in diameter T. tenuis 



(2) Filaments 9-12.5 mic. in diameter T. lanata 



(3) Filaments 10-15 mic. in diameter T. distorta 



(4) Filaments 12-17 mic. in diameter T. penicillata 



2 Plants living in moist places 



(i) Filaments 10-15 mic. in diameter T. byssoidea 



(2) Filaments 15-25 mic. in diameter T. ravenelii 



II Sheaths thick. 



1 Plants living in water 



(i) Filaments 5-6 mic. in diameter T. setchellii 



(2) Filaments 12-15 mic. in diameter T. limbata 



2 Plants living in moist places; filaments 12-15 mic. in diameter 



T. rupestris 



Species not well understood 



T. glacialis 



426. Tolypothrix tenuis Kuetzing. Phyc. Gen. 228. 1843. Bornet and Fla- 



hault. Revis. des Nostoc. Ann. Sci. Nat. Bot. VII. 5: 122. 1887. 

 De Toni. Syll. Algar. 5: 545- i907- 



