GLOEOTRICHIA. 245 



usually olivaceous, brown or reddish ; filaments closely 

 compacted and sometimes, apparently, one stratum on an- 

 other, the result of interrupted growths. The ends of the 

 trichomes suddenly acuminate ; cells, light aeruginous, 

 sheaths close, colorless, light yellow or brown, widened at 

 the ends and dissolved into fibrillse ; heterocysts colorless 

 globose or depressed. 



Single trichomes, separated from a mass, have a wide 

 sheath ; cells often distinct and rnoniliform. 



Diameter of filaments, 8-12 ju. 



Syn. Zonotrichia fluviatilis, Eab.; Mastigonema plana, Eab. ; Isac- 

 tisplana, Thur. 



Frequent on rocky margins of the bed of the Genesee 

 River, about Niagara Falls, and similar localities. 



Plate CLXXYII, figs. 5, 6, two small sections of the turf ; 

 figs. 7-10, isolated trichomes separated from the masses. 



ISACTIS CAESPITOSA, (Kg.) Wolle. 



Trichomes erect, awl-shaped, forming dark brown or 

 blackish, slippery coatings on submerged stones ; cells yel- 

 lowish green or brownish ; sheath close colorless ; primarily 

 closed, later open and often dissolved into fine fibrillae. 



Diameter of trichomes, 5-6 //, more or less. 



Syn. Mastigonema caespitosum, Kg. 



Plate CLXXVI, fig. 5, a very small section of a thallus. 

 Frequent on river stones in shallow water. 



Forma tenuior viridis, Eab. 



Forms deep olive, or almost black spots, larger or smaller 

 in size, with a smooth even surface, on pebbles and larger 

 stones near the shore of ponds. No appreciable distinction 

 between this and the type-form. Earely the trichomes are 

 linear. 



Plate CLXXVIII, figs. 1, 2, 3, from specimens collected 

 in northern Vermont and New Jersey. 



Plate CCV, fig. 6, section of thallus greatly magnified; 

 fig. 7, thallus moderately enlarged. 



Genus 84, GLOEOTEICHIA, Ag. 



Trichomes radiate, sometimes spuriously branched, distinctly 

 vaginate ; sheaths broad, often succate at the base, transversely 

 plicate, involved in a rather firm, more or less spherical mucus ; 

 spores originate in the lower part of the trichome. 



