140 FRESH-WATER ALG^ OF THE UNITED STATES. 



Genus 27, CONFERVA, Lk., including MICROSPORA, Thur. 



Filaments articulate, simple, like Ulothrix ; the two separated 

 with difficulty in sterile state. Cell walls more robust, cells as 

 a rule, longer, often swollen, and cell contents granular. 



Propagation by zoogonidia ; copulation has not been observed ; 

 microzoospores are produced by the division of the cell con- 

 tents; very numerous, small, ovate elliptical, cuspidate and 

 colorless at one end, furnished with two, or rarely three or four 

 ciliae, escaping by small pores, or ruptures of the cells. All 

 denizens of the water. 



CONFERVA AMOENA, Kg. 



Cheerful yellowish green ; cells primarily two diameters 

 in length ; after division equal. Cell membrane firm, often 

 finely striate. Filaments frequently three feet or more in 

 length, tenacious. Diameter of cells, 20-25 )J. ; the largest 

 of our Confervae. 



Not frequent, but in quantity where it does occur. Stream- 

 lets of spring waters. 



Plate XXI, figs. 1, 2, 3, normal vegetative condition in 



different stages of cell division ; fig. 4, older cells in state of 



dissolution, separating and distributing the cell contents 



-the niicrogonidia ; fig. 5, microgonidia seen under much 



higher power. 



CONFERVA FLOCCOSA, Ag. 



Cells more or less swollen, twice, or nearly twice as long 

 as wide ; variable in thickness. 



Diameter, 14-18 }JL. 



Syn. Microspora floccosa, Thuret; Lyngbya floccosa, Hass. ; 

 Conferva fugacissima, Dillw. 

 A common form. 



Plate CXX, figs. 21, 22, 24, ordinary condition previous 

 to division of cells ; figs. 23, 25, after division of cells ; 

 figs. 26, 27, cells of parts of filaments globular, formed into 

 extraordinary sporangial cells; figs. 28, 29, filaments in a 

 state of dissolution, membrane soft, mucous; cells green, 

 assume the form of macrospores ; farther development has 

 not been observed. Compare, Hormiscia, page 132. 



CONFERVA UTRICULOSA, Kg. 



Green or yellowish brown in soft mats ; cells before divi- 

 sion often six times longer than the diameter, distinctly con- 



