110 FRESH-W^ATER A L G il'] OF THE UNITED STATES. 



at the ends, which are truncate and often somewhat fuscous ; membrane very distinctly striate, 

 when empty somewhat fuscous; chlorophy! globules 5-7 (in each limb); vacuole placed in 

 the beut iii)ex, moderately large, including 12-20 corpuscles. 



Remarks. — The measurements given are those of Prof. Rabenhorst. Our Ame- 

 rican forms agree well with them. 



C. aiisii!!>lafiiiii, Ktz. 



C. gracile, sublineare, diametro 16-18 plo longius, ad polos levissimo attenuatum, apicibus late 

 truncatis; costis longitudinalibus paullulum prominulis 4-5, iuterstitiis eirciter jj^'" latis; 

 vesiculis chlorophyllaceis in quoque cruro 6-7 ; locello ab apice subremoto mediocri, corpus- 

 culis 12-20 impleto. (R.) 



Ztiam.—T^T"— A" = 0-00081"— 0.0010". (R.) 



Syn. — C. angustatum, Ktz. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 126. 



Hab. — In aquis quietis, prope Philadelphia, Peunsylvauia. Wood. Rhode Island. Bailey. 

 New Hampshire. (Lewis) 



C. slender, snblinear, 16-18 times longer than broad, very slightly attenuate at the ends, which 

 are broadly truncate ; with from 4-5 somewhat prominent longitudinal ribs, the interstices 

 about 555"' broad ; chlorophyl globules in each limb G-7 ; vesiclo subremoto from the apex, 

 moderate, containing from 12-20 corpuscles. 



C. jiincidiini, Ralfs. 



C. elongatum, anguste lineare, diametro 20-35 plo longins, leviter arcuatura, utroque polo vix 

 attenuatum ; apicibus truncatis ; cy tiodermate luteolo, interdum longitudinaliter striate. 



Diam.—^-i^-s" = .0004". 



Syn. — C. juncidiim, Ralfs. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 127. 



Hab. — In fossis. South Carolina. (Ravenel) In lacu Saeo, New Hampshire. (Lewis) 



Elongate, narrowly linear, 20-35 longer than broad, slightly bent, scarcely narrowed at the 

 ends ; apices truncate ; cytioderm yellowish-brown, sometimes longitudinally striate. 



Remarks. — I am indebted to Prof. Ravenel for specimens of this species, by 

 whom they were found on the slimy surface of a half dried-up ditch, associated 

 with numerous other desraids. The specimens are all smaller than the measure- 

 ments of Rabenhorst, but much larger than those given by Mr. Ralfs. None of 

 the plants have any chlorophyl granules — a circumstance probably simply depen- 

 dent upon the stage of their development. The longitudinal stria; are in none of 

 the specimens very distinct, and in many cannot be demonstrated. 



Since writing the above I have seen specimens collected by Dr. Lewis in " Saco 

 Pond," near the Crawford House, New Hampshire. 



Mr. Archer (Pritchard's Infus., p. 749) lays stress upon the fronds being straight 

 in the middle, with the ends curved downwards ; but I have seen numerous speci- 

 mens in which the curve was through the whole lensth. 



Fig. 2o, pi. 12, represents one of the specimens collected by Prof. Ravenel in 

 South Carolina. 



2. Cellulae cylindricx, dorso pZws minus convexw, venire subplanw, nunquam ventricoso 

 — injlalx. ' 



