44 DESMID.S OF THE UXITED STATES. 



0. ATTEXUATU3I, Ehrb. Plate IX, fig. 5. 



Somewhat curved, attenuated, suddenly contracted at the 

 end into a narrow conical point ; empty frond reddish, faintly 

 striated. 



Diameter 34-42 ix. 



I quote this diagnosis from Ralfs' Br. Desmids ; think we 

 ought to find, but am not satisfied that I had a genuine 

 species. 



C. STEIGOSUJI. Ehrb. Plate YTI, figs. 13, 14 ; and Plate LXIV, 

 figs. 9, 10. 

 Long fusiform, at the ends somewhat bent, 19-24 times as 

 long as broad, slightly tapering from the middle to the thin, 

 finely rounded apices. Vacuole small and indistinct. Cytio- 

 derm colorless, smooth. 

 Diameter 10-16 //. 



Pond waters, Pennsylvania and !N^ ew Jersey. Plate LXIV, 

 figs. 9, 10, represent a fruiting form, collected in abundance, 

 near Ocean Beach, July, '83. In form near C. parvu/um, but 

 proportionately so mucli longer than the species, I take it for 

 a variety of C. stj-igosum. Diameter of cells 10 u.; length 

 200 fi. ; twenty times longer than wide. 



SECTION III.— Cells more or less falcate ; dorsum and ventral margins both con- 

 vex, arched in the same direction, ends tapering. § A. form slightly curved. 

 5 B. forms strongly curved, sometimes almost semi-circular. 



C. STEioLATUM, Ehrb. Plate VII, figs. 8, 20. 



Cells slightly bent, S-16 times longer than broad, ends 

 reduced to one-fourth the largest diameter, aj^es obtusely 

 rounded. Vacuole full size, containing many active gran- 

 ules. Cytioderm of older forms, reddish brown, distinct 

 striate. Zygospore orbicular, smooth. 



Diameter, 30-48 fj.. 



Plate VI, figs. 5-S. Distinct from forms on Plate VI. 

 Fig. 8 may be considered of doubtful value. 



Frequent in shallow pools. 



I find three varieties, the one 6-8 times longer than broad 

 (.Plate VI, fig. 8 1 ; another 10-1.5 (Plate VI, fig. 20) ; and the 

 third only 4-5 times longer than broad. They may be recog- 

 nized as varieties, int'-rmrdbim, Ralfs; elongatum, Rab. ; and 

 tuiaidum, Rab. The latter is very near Nord's. xubcostatum. 

 The variety elongatum is more slender and more delicately 

 striate than the others. 



