48 DESMIDS OF THE UNITED STATES. 



>i :i riox IV. Cells falcate as the preceding; upper margin very convex, lower 

 side concave with a more or less conspicuous central Inflation, i-nds tapering. 

 Zygospores spherical, smooth. 



C. EHRENBERGII, Menegh. Plate VIII, fig. 16. 



Large, stout, five to six times as long as the central diam- 

 rtrr: upper margin very convex, lower side veutricosely 

 much inflated ; ends rounded ; cytioplusm with large gran- 

 ules, numerous, scattered; no striae, and no central suture 

 evident. Of the zygospore, Archer says, "it is smooth, 

 placed betweeen the slightly connected empty conjugating 

 fronds, the endochrome during the process of conjugation 

 emerging from the opened apex of a short conical extension 

 from the under side of each younger segment (or shorter 

 one) of each pair of recently divided fronds; the conjugat- 

 ing fronds being produced immediately previously by the 

 self-division of a pair of old fronds two sporangia (XYLIO 

 spores) being thus the ultimate produce of the two original 

 fronds." 



Diameter 75-110 n- Delp. 5<-79 ^. 



Ponds, Pennsylvania and New Jersey ; common. 



Var. IMMANE, Wolle. Plate VIII, fig. 17, similar to the typical 



form except in size. 

 Dameter 208 /*. 



Not infrequent in Budd's Lake, and larger ponds of New 

 Jersey. 



. ROBUSTUM, Hast. Am. Mic. J., July, 1892. 



Cells large, semi-lunar, a little more than four times as 

 long as wide ; cytioderm smooth : dorsum high convex ; 

 ventrum somewhat concave, ventricose ; chlorophyl globules 

 large, numerous scattered ; vacuoles large, terminal distinct, 

 with many moving granules. 

 Diameter 100-120 yw. 



Rochester, N. H., Dec., 1890. Had very much the appear- 

 ance of C. Ehrenbergii, with the ends less attenuated. 



C. MONILIFERUM, Ehrb. Plate VIII, fig. 16. 



Very near C. Ehrenbergii, but somewhat smaller, six to 

 nine times longer than broad, ends subacute; cytioderm 

 light straw-colored, smooth or finely striate ; large chloro- 

 phyllous granules in a single longitudinal series in the center 

 of the cell. 



Diameter 46-55 yw. 



