FRKSH-WATER ALGJi OF TUB UNITED STATE 8. 151 



e. T. tri-or quadriradiutc, processes short, usually colorless, sides somewhat concave. Spo- 

 rangium orbicular, beset with sjiincs ultimately brauched at the apex. L. tJVt" )" 

 B. ,1,". 



2. Semtcellula- triangular es ; anyuli non producti, obtnsi vel rotundati. 



,'nicelln trianyular ; the angles not produced, obtuse or rounded, 



M. piim tiilntum, Hutu. 



St parvum, pnnctulato-granulosum; semrcellnlis enormiter cllipticis, doreo lato rotuudatis, a 

 vertice triangular! bus ; angulis nun productis, obtuso rotuudatis ; latcribus uiudicu retusia. 



Diam. Lat. T ^ ff ," .001^". 



.S'yn. S. punriiildtum, ISutiiissoN. RALFS, British Dcsmidicse. RABENHOBST, Flora Europ. 

 Algarum, Sect. 111. p. 208. 



Hab. Pennsylvania ; Wood. 



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

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



/.'' mark*. This desmid is exceedingly common around Philadelphia, growing 

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

 fig. 10, pi. 13. 



M. rrenatum, BAILZY. 



St. duplo circitcr longins qnara latum, in medio utrinqnc exsectione profunda rotundata; 

 semicellnlis e basi cuneata flabclliforniibus, margiue superiore crenatis, a vertice triangular! bus, 

 angulis rotund ato-truncatis, crenatis, lateribus sinuatis glabris. (R.) Species nrihi iynota. 



Syn. St. crenatum, BAILEY. RALFS, British Desraidicte, p. 214. RABENHOBST, Flora Europ. 

 Algarum, Sect. III. p. 220. 



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



3. Semicellulet vertice 3-7 radiatee ; radii in apice plerumque bi- tri-fidi vel bi- tri- gpini. 

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



M. polymorphiim, BREB. 



St. semicellulis ellipticis, subtiliter grannlatis vel tennysime spinulosis, in medio mapis mintisve 

 inflatis, baud raro ventricosis, rectis, nonnunqiiain incurvis, ntrinque processn plus minus 

 elongato, lineari, in apice 3-4 fido vel apinulis 3-4 tenuissimis instructis, a vertice 3-45-6-7 

 radiatis, radiis achrois, ant trifidis ant rotnndatis, trispinis. (R.) Species mihiignola. 



,S'yn. St. polymorphum, BREBISSON. RALTS, British Desmidiem, p. 135. RABENOOBBT, Flora 



Europ. Algarnm, Sect. III. p. 209. 

 Dioni. Long. 0.001". Lat. 0.00087". (R.) 

 ll,ib. Florida; Bailey. 



Segments in f. v. broadly elliptic or almost circular, rough with minute grannies (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. cyrtocerniii. (St. cyrlocerum, BREB.) 



Majus, ad ,y, longnm, ficmicelltilis introrsum vontricosis, dorso late rotundatis, utrinque pro- 

 -u elongato, plerumque incnrvo apice bi- vel tri-cnnpidato instructis, a vertice triradiatis, 

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



