CLOSTERIUM. 41 



Not abundant, but turns up now and then with other forms, 

 in smaller ponds of Pennsylvania, New Jersey and Minnesota. 



Plate V, fig. 10, represents a large form and distinct va- 

 riety corresponding to description by Delpoute. Cytioderm 

 not longitudinally striate, but smooth and apices obtusely 

 rounded. 



Diameter 50-60 yw. 



Minnesota and New Jersey. 



C. DECUSSATUM, Kg. Plate VII, figs. 9, 10. 



Cylindrical, curvature scarcely appreciable ; 7-12 times 

 longer than broad ; very slightly tapering near the obtusely 

 rounded ends, cytioderm distinctly decussately striate. 



Diameter 20-25-30 /x 



Frequent in ponds, Mt. Everett, Massachusetts, August, 

 1882, and ponds northern part of New Jersey. Kiitzing of 

 Germany appears to have been the only individual who ob- 

 served this species. He sent a drawing to Ralfs, but he ques- 

 tioned the correctness of his friend's vision ; he remarks, 

 " Prof. Ku'tzing represents the striae as regularly crossing each 

 other, so as to form diamond-shaped reticulations. As this 

 appearance is not unusual in dried specimens, when the 

 flattened cell permits the striae of both surfaces to be visible 

 together ; I will venture to suggest the possibility that Prof. 

 Kutzing's drawing may have been taken from a cell in that 

 condition." 



The correctness of Kiitzing's observations is readily estab- 

 lished by an examination of the plants as found in Gilder 

 and other ponds on Mt. Everett. They are cylindrical and 

 may be rolled over to display the decussated striae on every 

 side alike. 



C. ANGUSTATUM, Kg. Plate VII, figs. 21, 22, 23. 



Cells subliuear, 16-18 times longer than wide, very slightly 

 attenuated ; ends obtusely rounded. Cells present 4-5 some- 

 what prominent longitudinal striae ; 2 or 3 transverse bands 

 or striae are also frequently distinct ; vacuole subremote 

 from the apex, small. Dried specimens brownish yellow. 



A variety is frequent with the striae loosely crossing each 

 other, decussately. 



Diameter 15-25 ^. 



Ponds, Berkshire Mountains, Mass. 



