134 FRESH- WATER ALGJ3 OF THE UNITED STATES. 



equal, or half as long as wide ; fructiferous cells usually a 

 little longer than broad, slightly constricted at the joints. 



Diameter of filaments, 14-40 u. 







Diameter of macrozoospores, 12-18 yu. 

 Diameter of microzoospores, 4-7 //. 



In vegetative state of bright green color, affecting cold and 

 rapid waters, firmly attached to stones, two to six inches 

 long. Foreign authors describe it as found in floating, inter- 

 woven masses. As such have not seen it. The largest 

 growth and greatest quantity occurred later in the season, 

 in sluggish and warmer water; had a dull yellowish green, 

 faded color; it was attached to stones in the bottom, ascend- 

 ing to the surface, one to two feet long. 



Syn. Hormiscia zonata, Aresch. ; Lyngbya zonata, Hass. ; Conferva 



zonata, Ag. Syst. ; Conferva lubrica, Dillw. 

 Plate CXVII, figs. 1, 2, 3, filaments in ordinary vegetative 

 condition ; fig. 4, part of a filament with one macrozoospore 

 in each cell ; fig. 5, one escaping, and two free macrozoo- 

 spores with four ciliae ; fig. 6, macrozoospores, one at rest 

 germinating, and three having already developed a number 

 of cells ; fig. 10, cells with ripe microzoospores, some in 

 cells, others escaped ; fig. 11, microzoospores passing out of 

 cells, in a cyst ; fig. 12, the same separated and at rest ; figs. 

 13, 14, part of a filament with microzoospores germinating 

 in the cells, without having copulated ; figs. 15, 16, resting 

 zygospores, the result of two macrozoospores conjugating; 

 the three in different stages ; figs. 17-19, microzoospores con- 

 jugating ; two fertilized. 



ULOTHRIX .EQUALIS, Kg. 



Filaments yellowish green, articulations as long or some- 

 what longer than the diameter, (12-14 yu), not constricted at 

 the septae ; cell-membrane rather thick. 



Attached to plants in shallow river waters. Very near if 

 not identical with U. Juergensii, Kg. 



Plate CXVIII, figs. 3, 4, 5. 



ULOTHRIX TENUIS, Kg. 



Dark green, attached ; from half to two or three inches 

 long, mucous, cells equal, to two, to four times shorter than 

 the diameter ; cell-membrane thin, homogeneous. 



Diameter of filaments, 17-25 yw, 

 Plate CXVIII, figs. 1, 2. 



