I InsTKlMl'M. \] 



C. A.CEROH1 \i. (Schrank) Ehrb. Plate VI. figs. 7, 11. 



Linear fusiform, or slightly curved, 1524 times longer than 

 wide, lightly tapering towards the ends; apices narrowly trun- 

 cate, or obtusely rounded, transparent <r yellowish ; cytioderm 

 rather indistinctly, or n<>t at all striate. Chlorophyl globules 

 11-1 t arranged in a simple axillary series in each semi-cell; 

 vacuole small with numerous corpuscles. Zygospore globose. 

 Diameter variable, 3562 /. ' 



One of our rnosl common species, often forming gelatinous 

 floating masses on small ponds and pools. I have it from 

 many States, and probably il exists in every one. 



The entire chlorophyl of this species often retracts itself 

 from tlif cell-wall and breaks up into a number of oval <r 

 globular forms, every one of which acquires a firm envelope. 

 Plate VIII. fig. 17, represents one of these forms. 



( '. nasi il m. Nord. Plate V I. Kg. 12. 



Large, fusiform, only slightly curved, about five times as 

 long a- wide, gradually tapering from the middle to near the 

 ends, then suddenly contracting, making the sides parallel, to 

 the truncate <r rounded apex. Cytioderm smooth. 

 I hameter 75 u. more or less. 



Ponds, Berkshire Mountains, Massachusetts. 

 The only counterpart t" thi> form, hitherto found, i> from 

 Brazil, and is represented in Witt, and Nord's Alga Elxsiccatu 

 No. 366. 



( '. turgidi \i. Ehrb. Plate V I, fig. 1">. 



Dorsum convex, lower margin somewhat concave, inclining 

 upward at the rounded ends; upper margin with a depression 

 near each extremity ; empty cells reddish brown, striae 

 numerous, t i 1 1 < but distinct. 

 Diameter <> 175 ". 



Wet. marshy places, Pennsylvania. 



( . ATTKM am \i. Ehrb. Plate V I I I , fig. 5. 



Somewhat curved, attenuated, suddenly contracted at the 

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

 striated. 



Diameter 34-4*2 />. 



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

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



