DOCTDIUM. 4. 



C. Kuetzingh, Breb. Plate VIII, fig. 8. 



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

 late, each extremity tapering into a long slender setaeous beak 

 which is curved :it the obtuse ends, ami less than the length of 

 the body. 



I tiameter in middle 1 7 u. 



Rather rare in ponds, Pennsylvania and New Jersey. 



C. Abtaceum, Ehrb. Plate VIII. figs. 6, 7. 9, 10, 1 1. 



Very -lender. Smaller than the preceding; 2025 times 

 longer than broad, upper and lower margins equally convex ; 

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

 enlarged :it extremities, longer than the length "t' the body ; 

 striae close, hum . central -mure solitary. Zygospore cruciform. 



Diameter I" I I . 



Frequent in Pennsylvania, Ken Jersey, Massachusetts, 

 etc. Solitary and conjugating. Bailey reports it From 

 Rhode Island, < reorgia and Florida. 



Genua, DOCIDIUM, Breb. 



Cells straight, cylindrical or fusiform, elongated, apices rounded, 

 truncated or divided ; transverse view circular; constricted at the 

 middle, with or without :i suture between the semi-cells which are 

 usually inflated at the base. 



Docidium, like 4 'losterium, has in most instances terminal vacuoles 

 which contain numerous "dancing granules The pie- nee or 

 absence of these vacuoles, and the arrangement of the chlorophyllous 

 cytioplasm, whether parietal or axillary, have heen made points for 

 generic separation between otherwise similar forms. These dis- 

 tinctions seeming too uncertain and variable in different stages of 

 growth, I put them all together, and retain Docidium in prefer- 

 ence to Pleurotoenium, as the older name. 



D. crenujlatum, (Ehrb.) Rab. (Pleurotaenmm nodulomm. I >. By. 



Docidium nodulomm, Etalfs.) Plate IX. fig. 1. 

 (ell very stout, the thickened sutures forming a projecting 

 rim ; 8-16 times longer than broad, scarcely attenuated ; regu- 

 larly inflated at interval- so as to form an undulated margin ; 



