STIGEOCLONIUM. 113 



lations cylindrical or swollen, often hyaline, 2-6 times longer 

 than broad; chlorophylous contents scattered, or collected 

 into narrow bands ; branches flagelliform, opposite, on 

 distinct cells, shorter and more oval than the others of the 

 filaments, erect patent ; sometimes the cell with a pair of 

 branches is single, sometimes 2 or 3 are in close connection ; 

 articulations intervening are nude; secondary branches 

 short, flagelliform, ends piliferous. 



Var. CRASSIUSCULUM, Kg. 



A larger and more robust form. 



Diameter of basal cells, typical form, 12-16 /*. 

 Diameter of basal cells, variety, 18-25 yu, the latter con- 

 siderably swollen. 



The former collected by Dr. Hobby, in sluggish streams, 

 Iowa; the latter from a rapid mountain stream, Carbon 

 County, Pennsylvania. 



The diagnosis is somewhat modified to adapt it to our 

 American forms. 



Plate XCVII, fig. 1, the Iowa plant ; fig. 2, the Pennsyl- 

 vania plant. 



STIGEOCLONIUM AMCENUM, Kg. 



Bright green, about half an inch long, caespitose ; 

 branches mostly opposite, fasciculately branched, short, 

 subulate, not piliferous ; diameter of articulations 12-17 yw 

 3-8 times longer ; in upper part of filaments, cylindrical ; 

 in basal part, often considerably swollen ; chlorophylous 

 contents of cells thin, usually centrally concentrated. 



Mountain springs and pools, Pennsylvania. 

 Plate XCYIII, fig. 4. 



STIGEOCLONIUM NUDIUSCULUM, Kg. 



Caespitose, floccose, bright green, about half an inch long, 

 lubricous ; basal part of filament, 25-40 ^ in diameter ; 

 articulations 1-2-3 times longer than broad, always some- 

 what swollen ; constricted at joints ; epidermis sometimes 

 plicate at joints ; lower branches often single, upper ones 

 opposite and simple, rarely with secondary branchlets, 

 patent, short, tapering, apex acute piliferous. 



Attached to stones in a rapid mountain streamlet, Monroe 

 County, Pennsylvania. 



Plate XCVIII, figs. 1, 2, nearly a full length of plant ; fig. 

 3, the upper end of another, and a part of a third in which 

 the contents of the cells have developed zoospores. 



