PENIUM. 37 



P. POLYMOEPHUM, Pei'ty. Plate V, fig. 12. 



Sub-cylindrical, smooth, various sizes usually intermingled 

 in larger families ; 3-4 times longer than broad, ends more 

 or less attenuated, apices rounded ; cytioderm somewhat 

 longitudinally striated. 



Diameter 11-15 /<. 



Pools, or wet earth, Charlotte, Vermont. Collected by F. 

 Hosford. 



P. Brebissonii, (Menegh.X Ralfs. Plate V, figs, 7, 8. 



Cells smooth, cylindrical with rounded ends, transverse 

 central band inconspicuous ; conjugating cells persistent. 

 Diameter 16-17 yu. 



Usually congregated ia a mucous stratum in small pools 

 and on wet grounds, Princeton, New Jersey (Bailey) and other 

 localities in the State. The plant mentioned by Wood ap- 

 pears to be nearer Closterium obtusum, Breb. 



P. Navicula, Breb. Plate V, fig. 16. 



Small, broadly fusiform, 4-5 times longer than broad, 

 tapering from the center to the rounded apices. Chlorophyl 

 lamina entire ; cytioderm smooth. 



Diameter 12-17 fA. 



Zygospores are said to be nearly square, somewhat drawn 

 out between the attached remains of the copulating cells. 

 The plant occurs frequently in trenches and small ponds of 

 Pennsylvania and New Jersey ; the fruiting cells, or zygo- 

 spores have not come under my personal observation. 



P. Jenneei, Ealfs. Plate SXXVII, figs. 1, 2. 



Smooth, cylindrical with rounded ends, zygospores orbic- 

 ular, situated between the conjugating cells which are 

 deciduous. 



Diameter 14-15 /<.' 



I have not recognized this form. Bailej' reports it from 

 Florida. Eabenhorst describes It as scarcely distinguishable 

 from P. Brebissonii; 2J-5 times longer than broad ; zygospores 

 mostly globose, membrane somewhat fuscous, sub-granulate. 



P. CEASSA. D. By. Plate V, fig. 3. 



Cells short, ovate-cylindrical, lJ-2 times as long as wide, 

 chlorophyl not separated, but concentrated into two or more 

 nuclei in each cell. 

 Diameter 25-29 /a. 



Colli'cted by E. 8. Cheeseman, Knowlesville, New York, 

 in gi.'latinou8 mucus in an aquarium. 



