times the diameter in length (in our specimens, with cells separated 

 slightly from each other), with a conspicuous granule at each cross 

 wall, contents not vacuolate; heterocyst subglobose to elongate- 

 elliptic or ovate; gonidia short-cylindric, 14.8ju in diameter, 27,3- 

 (44) fx. long with a yellowish membrane. 



The plant, found but once, is scantily represented in the collec- 

 tion. The characteristics are distinctive, however, and agree closely 

 vdth the description given by West; hence it is tentatively assigned 

 to Gloeotrichia longiarticulata G, S, West, Subsequent collections 

 are needed to confirm this identification. 



Attached to submerged aquatics. Wis. 



Gloeotrichia natans (Hedwig) Rabenhorst 1847, p. 90 

 PI. 134, Figs. 6, 7 



A soft, gelatinous, globose or bullate, attached colony, brown or 

 olive-green in color, becoming free-floating and expanded to form 

 irregularly shaped mucilaginous masses at maturity; filaments at 

 first somewhat radiate, becoming irregularly arranged and entangled, 

 very long and tapering from a basal heterocyst; cells barrel-shaped 

 or subglobose below, becoming quadrate or subcylindrical distally, 

 7-10/x in diameter; heterocysts globose or ovate, 8-12/x in diameter; 

 gonidia solitary, adjacent to the heterocyst, 12-18/a in diameter, up 

 to 250/x long, with a thick wall and a sheath; basal sheath of the 

 filament covering about a third of the length, lamellated, wrinkled, 

 wide and funnel-shaped above. 



This species forms attached colonies as much as 10 cm. across 

 under favorable conditions (quiet hard water and high tempera- 

 tures). The mucilage is very soft, and the colonies expand and be- 

 come floating masses by the time gonidia have reached maturity. 

 Inasmuch as the plant mass soon fragments, this species is frequently 

 collected in plankton catches, where it appears as irregular flakes 

 of entangled filaments. Under such circumstances it may be differ- 

 entiated from old colonies of Gloeotrichia echinulata by the form 

 of the sheath, the larger size of the gonidia, and by the greater 

 length of the flagelliform trichome. At maturity the vegetative cells 

 dissociate, leaving the spore and the heterocyst adjoined. 



Common in many hard or semi-hard water lakes. Mich., Wis. 



Gloeotrichia Pisum (C, A. Ag,) Thuret 1875, p. 382 

 PI. 134, Figs. 8-10 

 A firm, mucilaginous, brown or olive-green, globular or hemispher- 

 ical colony, attached to submerged aquatics; colonies from 1 mm, to 

 1 cm, in diameter (usually about 5 mm,), composed of compactly 



[559] 



