214 FRESH-WATER ALG.E OF THE UNITED STATES. 



SPIROGYRA LONG ATA, (Vauch.) Kg. 



Diameter of filaments, 25-30 ^ ; cells 2-12 times longer 

 than broad ; fructiferous cells not swollen or rarely moder- 

 ately inflated ; spiral rather large, bright green, describing 

 2-5 turns. Zygospore oval, ends rounded, twice as long as 

 wide, filling the breadth of the cell, changes color from 

 green to light yellow and chestnut. 



Syn. Conferva longata, Vauch. ; Zygnema longatum, Ag. ; Zygnema 

 aestivum, Hass. 



The three preceding forms 8. commune, Jurgensii, and 

 longata, seem closely related; 8. quinina is also near, but 

 separated by features which have been deemed sufficient 

 to mark distinct species. 



If the occurring varieties are taken as typical forms then 

 a separation would prove impossible. Spirogyra filaments 

 of the same species often vary very much in diameter, in 

 length of cells, number of turns and width of spirals, and 

 shade of color. The length of cells is constantly changing 

 by division ; the number of spirals is not absolutely con- 

 stant ; there are sports, so called ; conjugation of filaments 

 of different species have been observed, but such occasional 

 deviation from rule must not be taken as a guide in classifi- 

 cation. The features as they appear in mass have been our 

 guide. 



Occurs frequently in masses in ponds, mill-dams, etc. 

 Plate CXXXV, figs. 9, 10, sterile, and conjugated fila- 

 ments. 



SPIROGYRA LUTETIANA, Petit. 



Diameter of vegetative filaments, 30-36 fji (mine 40-43 /*). 

 Cells 3-7 times longer than the diameter ; spiral single, 

 large, dentate, deep green, describing 3-7 turns ; sporiferous 

 cells irregular, always more or less inflated, sometimes 

 cylindrical. Zygospores polymorphous, globose, elliptic, 

 oblong, cylindric, pyriform or reniform, of yellow tint when 

 mature, 2-4 times longer than wide ; diameter, 30-42 JA. 



A plant gathered in considerable quantity, mostly sterile, 

 in lake at Kissimmee, central part of Florida, is not iden- 

 tical with the one described above by Mons. Petit, but in 

 size and proportions of cells and general appearance so much 

 like it, and so unlike any other described form, have adopted 

 this name for it. 8. fusco-atra, Rab., is closely related, but 

 varies in length of cells, number of turns of spiral in cells, 

 and less inflated fruit-bearing cells. 



Plate CXXXY, figs. 7, 8, a sterile, and fertile filaments. 



