50 DESMIDS OF THE UNITED STATES. 



Ponds, Massachusetts. J. R. M. 8., Nov., 1888. 



Frequent in ponds, Pennsylvania, New Jersey, Vermont, 

 Connecticut, Florida. 



In this vicinity, Bethlehem, Pa., copulating specimens are 

 of common occurrence. 



C. PBONUM, Breb. Plate VI, fig. 22. 



Cells very small, sublanceolate, each end drawn out into 

 a setaceous beak about half as long as the body ; cytioderm 

 finely striate. 

 Diameter 7-12 yw. 

 Ponds, Florida. 



C. KUETZINGII, Breb. Plate IX, fig. 8. 



Straight in the middle, smaller than the last, narrow lan- 

 ceolate, each extremity tapering into a long slender setaceous 

 beak, which is curved at the obtuse ends, and less than the 

 length of the body. 

 Diameter in middle 17 v. 



Rather rare in ponds, Pennsylvania and New Jersey. 



C. SETACEUM, Ehrb. Plate IX, figs. 6, 7, 9, 10, 11. 



Very slender. Smaller than the preceding ; 20-25 times 

 longer than broad, upper and lower margins equally convex ; 

 ends tapering into long seta-like beaks, colorless, somewhat 

 enlarged at extremities, longer than the length of the body ; 

 striae close, faint, central suture solitary. Zygospore cru- 

 ciform. 



Diameter 10-11 n. 



Frequent in Pennsylvania, New Jersey, Massachusetts, etc. 

 Solitary and conjugating. Bailey reports it from Rhode 

 Island, Georgia, and Florida. 



Genus, DOCIDIUM, Breb. 



Cells straight, cylindrical or fusiform, elongated, apices 

 rounded, truncated or divided ; transverse view circular ; con- 

 stricted at the middle, with or without a suture between the 

 semi-cells which are usually inflated at the base. 



Docidium, like Closterium, has in most instances terminal va- 

 cuoles which contain numerous "dancing granules." The pres- 

 ence or absence of these vacuoles, and the arrangement of the 

 chlorophyllous cytioplasm, whether parietal or axillary, have 

 been made points for generic separation between othenvi>r 

 similar forms. These distinctions seeming too uncertain and 



