46 DESMIDS OF THE UNITED .TATES. 



Occurs occasionally in sluggish waters, Pennsylvania and 

 New Jersey. This form is separated from C. strioiatum, 

 mainly by the larger number of striae ; the one has 12-15 and 

 the other 20-30. 



C. AREOLATUM, Wood. Plate VIII, figs, 3, 4. 



Fusiform, straightish, or very slightly curved, the ventral 

 side often a little concave in the middle ; 9-10 times longer 

 than broad, moderately attenuated at each end ; the apices 

 truucately rounded; cell-membrane reddish brown, thick 

 and firm, distantly profoundly striate, and very minutely 

 but distinctly granulate or areolate ; median sutures very 

 distinct, 4-10 in number. 

 Diameter 60 //. 



Dr. Wood remarks : " I found this species growing in a 

 quiet pool of pure water, in a wild, deeply wooded ravine, 

 near Danville, Central Pennsylvania. It was in great abund- 

 ance, forming a translucent greenish jelly, one or two gills of 

 which might have been readily gathered." "This species is 

 very closely allied to C. turf/id <nn, Ehrb., agreeing pretty well 

 with it in general outline and size. I think, however, the 

 peculiar markings upon the membrane are sufficient to sepa- 

 rate it." "The turning up of the ends, generally so marked 

 in C. turgid um is mostly entirely absent in this species, rarely 

 there is some tendency to it." 



C. SUBDIRECTUM, West. Plate LIV, fig. 20. 



Frond about fifteen times longer than broad, gently taper- 

 ing, the middle portion nearly straight, slightly curved near 

 the ends, which are truncate with rounded corners, cytio- 

 derni finely striate, with three distinct transverse sutures. 

 Diameter 26-27 p. ; length 390-400 ju. 



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



C. AMBLYONEMA, Ehrb. 



A form bearing this name was accredited to the United 

 States by Dr. Ehrenberg. Prof. Bailey, about thirty years 

 since, examined the character of the plant, and pronounced 

 it the same as C. lineal um. 



C. ACUTUM, Breb. Plate VIII, figs. 11, 12. 



Small, slightly bent, 6-12 times longer than broad, gently 

 tapering from the middle to the rounded ends ; cytioderm 

 colorless and smooth. Zygospores angular. 

 Diameter 9-11 p. 



Not rare in marsh pools, Pennsylvania and New Jersey. 



