216 FRESH-WATER ALGJ3 OF THE UNITED STATES. 



attaches itself to the surface of the opposite cell ; the chloro- 

 phyl passing over, the spore is formed and the cell becomes 

 much inflated. 



The only locality hitherto discovered for this species is 

 Pleasant Mills, New Jersey. 



Plate CXLI, figs. 5, 6, 7, four fertile and one sterile fila- 

 ment. 



B. Tivo or more spirals. 



SPIROGYRA DECIMINA, (Mull.) Kg. 



Diameter of vegetative filaments, 32-40 /* ; cells 2-4 times 

 longer than the diameter 5 two spirals (rarely three) rather 

 large, describing 1-2 turns ; fructiferous cells not inflated ; 

 zygospore broadly oval or nearly globose ; same diameter as 

 filament. 



As a rule this species has two spirals, but occasionally 

 three ; being found intermingled, and having a specific ap- 

 pearance, the latter are not easily confounded with other 

 species of the same number (three) of spirals. Often found 

 in large masses, mucilaginous to the touch. 



Syn. Conferva decimina, Mull.; Zygnema deciminum, Hass. 

 Plate CXXXV, figs. 5, 6, sterile and fruiting filaments. 



SPIKOGYRA NEGLECTA, (Hass. ) Kg. 



Diameter of vegetative filaments, 60-65 // cells 2-5 times 

 longer than broad; three spirals describing 1-2 i turns; 

 sporiferous cells li-3 times longer than the diameter, 

 slightly swollen ; zygospores oval, ends broadly rounded, 

 yellow at maturity, about one-half longer than the diameter. 



Kiitzing notes a peculiar feature in the spirals of this 

 species he says they are cylindrical and possess a sort of 

 central nerve. Rabenhorst and others consider this feature 

 of uncertain and doubtful value. My specimens were 

 collected in South Carolina and reaching me in a partially 

 dried condition could form 110 opinion. Was governed in 

 my identification chiefly by the proportions of cells and 

 spirals. 



Syn. Zygnema neglectum, Hass. 



Plate CXXXVI, figs. 8, 9, fruiting and sterile filaments. 



SPIROGYRA FLUVIATILIS, Hilse. 



Diameter of vegetative filaments, 33-38 ^ ; cells 3-6 times 

 as long as broad; four spirals; wide and usually dense, 

 bright, rather dark green, describing 1-2 turns. Fruc- 



