MASTIGONEMA. 243 



seta ; internal filament shortly articulate, minutely granular, 

 continuous or variously interrupted ; sheath firm, rather 

 thick, often distinctly lamellated, colorless ; heterocysts 

 subglobose. 



Diameter with sheath, about 12 /u. 



An inhabitant of salt or at least brackish water. Have 

 found its like in fresh water also. 



Plate CLXXIV, fig. 2, the growth, under low magnifica- 

 tion ; fig. 1, the plant enlarged 250 diameters. 



MASTIGONEMA SEJUNCTUM, Wood. 



Thallus somewhat caespitose, soft, parasitic; filaments 

 simple, mostly inarticulate, but sometimes shortly, some- 

 times long articulate, attenuate at the apex, yellowish olive 

 or greenish, sparsely granulate ; sheaths mostly ample and 

 distinct hyaline, often strongly undulate, the apex mostly 

 much amplified and dissolved into fibrillae ; heterocysts 

 about equal to diameter of the filaments. 



Diameter of trichonie, 4 yw. 

 Diameter of sheath, 12 yu. 



Growing on the edges of minute leaves, so as to form little 

 prominences or thickenings of the margin. Carp River bog. 



Plate CLXXIII, fig. 9, a small tuft ; fig. 6, an isolated 

 trichome. 



MASTIGONEMA ELONGATUM, Wood. 



Thallus at first subglobose, afterwards frequently fusiform, 

 blackish green, slippery, firm ; filaments aeruginous, very 

 elongate, sometimes not articulate, but more generally 

 shortly articulate, sometimes strongly contracted at the 

 joints ; apices sometimes truncate, but generally produced 

 into long, flexuous, translucent hair-points ; sheath trans- 

 parent, close, frequently truncate at the apex ; heterocysts 

 globose or subglobose. 



Diameter of filaments, 6-7 yw. 



Was found growing in an aquarium on some brook moss. 

 It forms little nodules of the size of a pin's head upon the 

 wire-like stems, or sometimes longer fusiform masses which 

 are apparently produced by the coalescence of the little glob- 

 ules. The color of these fronds, which are very firm, is 

 blackish green. The filaments radiate from the base in all 

 directions, etc. Wood. 



Evidently not a Mastigonema, but a Rivularia. 

 Plate CLXXIY, fig. 9, a single filament, after Wood. 



