FRESH-WATER ALG^ OP THE UNITED STATES. 151 



e. V. tri- or quadriradiate, processes short, usually colorless, sides somewhat concave. Spo- 

 rangium orbicular, beset with spines ultimately branched at the apex. L. xsVs" sh"- 



Bi " 



2. Semicellulse triangulares ; anguli non producti, obtusi vel roiundati. 

 Semicells triangular ; the angles not produced, obtuse or rounded. 



St. punctnlatum, Br£b. 



St. parvum, punctulato-granulosum ; semrcellnlia enormiter ellipticis, dorso late rotundatis, a 



vertice triangularibus ; angulis non productis, obtuse rotundatis ; lateribus modice retusis. 

 JDiam.—L&i. ^jVir" = -0012". 



Syn. — S. punctulatum, Brebisson. Ralfs, British Desmidieae. Rabenhorst, Flora Europ. 

 Algarum, Sect. III. p. 208. 



Hab. — ^Pennsylvania ; Wood. 



Small, punctulate-granulate ; semicells irregularly elliptic, with the dorsum broadly rounded 

 from the vertex triangular ; angles not produced, obtusely rounded ; sides somewhat retuse. 



Remarks. — This desmid is exceedingly common around Philadelphia, growing 

 in the greatest abundance upon the face of wet dripping rocks. It is represented, 

 fig. 10, pl.l3. 



St. crenatum, Bailey. 



St. duplo circiter longius qnam latum, in medio utrinque exsectione profunda rotundata ; 

 semicellulis e basi cuneata flabelliformibus, margine superiore crenatis, a vertice triangularibus, 

 angulis rotundato-truncatis, crenatis, lateribus sinuatis glabris. (R.) Species mihi ignota. 



Syn. — St. crenatum, Bailey. Ralfs, British Desmidieae, p. 214. Rabenhorst, Flora Europ. 

 Algarum, Sect. III. p. 220. 



"Segments cuneate; outer margins crenate; end view with three truncate and crenate angles." 



3. Semicellulx vertice 3-t radiatse ; radii in apice plerumque bi- tri- fidi vel bi- tri- spini. 

 Semicells 3-7 radiate at the vertex ; radii bi- or tri-fid, or bi- or tri-spinous at the apex. 



St. polymorphum, Breb. 



St. semicellulis ellipticis, subtiliter granulatis vel tenuissime spinulosis, in medio magis minusve 

 inflatis, baud raro ventricosis, rectis, nonnunquam incurvis, utrinque processu plus minus 

 elongato, lineari, in apice 3-4 fido vel spinulis 3-4 tenuissimis instructis, a vertice 3-4-5-6-7 

 radiatis, radiis achrois, ant trifidis aut rotundatis, trispinis. (R.) Species mihi ignota. 



Syn. — St. polymorphum, Br£bisson. Ralfs, British Desmidie®, p. 135. Rabenhorst, Flora 



Europ. Algarum, Sect. HI. p. 209. 

 Diawi.— Long. 0.001". Lat. 0.00087". (R.) 

 ffab. — Florida; Bailey. 



Segments in f. v. broadly elliptic or almost circular, rough with minute granules (sometimes 

 with a few minute scattered spines), processes short, stout, tipped by three or four divergent 

 spines ; e. v. with three, four, five, or six angles each produced into a short, stout process. 

 Sporangium orbicular, beset with elongate spines, forked or branched at the apex. Archer. 



Far. cyrtocerum. (St. cyrtocerum, Br^b.) 

 Majus, ad jV", longum, semicellulis introrsum ventricosis, dorso late rotundatis,. utrinque pro- 

 cessu elongato, plerumque incurvo apice bi- vel tri-cnspidato instructis, a vertice triradiatis, 

 radiis rectis vel leniter curvatis, in apice aut bi- aut tri-cuspidatis. (R.) 



