SCYTONEMA. 259 



broad; sheaths thick, brownish or almost colorless, often 

 incrusted with a granular deposit of lime. 



Diameter of vegetative cells, 3-10 ^ ; sheaths 9-20 //. 

 Syn. Scytonema Julianum, Wittr. and Nord. ; Drilosiphon musci- 

 cola, Kg. ; Oscillaria cyanea, Hass. ; Humida cyanea, Gray. ; 

 Scytonema pulverulentum, Ag., etc. 

 On moist rocks, shaded walls and the like. 

 Plate CLXXXVIII, figs. 1-4, from rocks, New Jersey and 

 Pennsylvania ; figs. 10, 11, 12, from New York State ; figs. 

 13, 14, from Florida. 



SCYTONEMA THEUMALE, Kg. 



Stratum thin, blackish ; filaments ftexuously curved, in- 

 tricate, sparingly branched ; internal filament pale greenish, 

 often almost colorless, here and there interrupted, mostly in- 

 articulate, but often indistinctly and sometimes distinctly 

 articulate, granular ; joints shorter or about as long as 

 broad ; branches geminate, mostly short, equal or unequal to 

 the filaments in diameter, coalescent at the bases, rarely so 

 even to their middle ; sometimes divergent from the base ; 

 sheath thick, indistinctly lamellate, yellowish fuscous and 

 scarcely semi-transparent, but here and there nearly color- 

 less and pellucid ; generally so at the apices of the branches ; 

 heterocysts subquadrate or cylindrical, singly interspersed. 

 Internal filament less than one-half as thick. 



Diameter of filaments, with sheath, 10-14 yw. 



Dr. Wood recognized this species from sandy soil, near 

 Aiken, South Carolina. 



SCYTONEMA SIMPLICE, Wood. 



Forms moderately thick, somewhat tomentose, blackish 

 green strata; trichomes very elongate, flexuously curved, 

 very sparsely branched or frequently without branches ; 

 branches geminate or single, mostly elongate ; internal fila- 

 ment partly distinctly articulate, partly inarticulate, gran- 

 ular, pale greenish, in its apex sometimes very shortly 

 articulate, sparsely granular, often nodose or disjoined at 

 the joints; articles mostly equal to seven times longer than 

 the diameter; sheaths thick, transparent, often colorless, 

 sometimes pale yellowish brown, mostly open and truncate 

 at apex ; heterocysts cylindrical, interspersed, 2-5 times 

 longer than their diameter. 



Diameter of trichomes, with sheath, 10-15 /* without 

 sheath, 3-6 JJL. 



