148 FRESH-WATER ALG^ OF THE UNITED STATES. 



A. CtTIODERMA LffiVE VEL RAEISSIME SUBTILITEK PUNCTATUM. 



Cytioderm smooth or very rarely very finely punctate. 



1. Semicellularum anguli rotundati. 

 Angles of the semicells rounded. 



St. mnticnm, Breb. 



St. a fronte orbiculare, laeve, profunde constrictum, nudum, vel rauco plus minusve firmo invo- 

 lutum ; semicellulis ellipticis, a yertice conspectls 3-4 angularibus (rarius quinquangularibus)' 

 angulis rotundatis, lateribus leviter sinuato-retusis ; zygosporis aculeatis, aculeis elongatis, 

 subnlatis, furcatim fissis. (R.) Species mihi ignota. 



Diom.— 0.0013"— 0.00014r'. (R.) 



Syn. — S. muticum, Brebisson. Rabenhorst, Flora Europ. Alg&r., Sect. III. p. 200. 



ffab. — South Carolina ; Rhode Island ; Bailey. 



Segments in f. v. elliptic, smooth, without spines ; e. v. with three or four broadly rounded 

 angles, sides concave. Sporangium beset with numerous elongate somewhat stout spines, 

 forked at the apex. (A.) 



St. orbiculare, (Ehrb.) Ralfs, 



St. snborbiculare, lasve, ssepius muco matricali involutum ; semicellulis divergentibus, semi. 

 orbicularibus, dorso nonnunquam elevatis, angulis plus minus late rotundatis, lateribus plus 

 minus sinuato-retusis ; zygosporarum aculeis elongatis, subnlatis, integris. (R.) 



Diam— .002". 



Syn. — iSi!. orbiculare, (Ehrb.) Ralfs, British Desmidieee, p. 125. Rabenhorst, Flora Europ. 

 Algarum, Sect. III. p. 200. 



Sab. — Rhode Island ; Bailey. Pennsylvania ; Wood. Rhode Island ; (S. T. Olney) Thwaites. 



- Segments in f v. semiorbicular, smooth, without spines ; e. v. with three broadly rounded angles, 

 sides slightly concave. (A.) 



BemarJcs. — Fig. 17, pi. 21, represents the outline of the end vievr of a frond of 

 this species. Fig. 8, pi. 13, is a drawing of the front view of a living frond. 



2. Semicellularum anguli mucronati vel aristati. 

 Angles of the semicells mucronate or bristly. 



St. long^ispinum, (Bailey) Archer. 



St. magnum triangulare, l^ve, angulis in acnleos geminos valid^ subulatos longe productum, 

 lateribus subplanum. (R.) Species mihi ignota. 



Syn. — Didymocladon longispinum, Bailey, Microscopical Observations. 



Sab. — Florida; Bailey, 



"Large, smooth, triangular, with two long spines at each angle." Bailey. 



St. dejectnm, Brebisson. 



St. laeve, parvum, sinu amplo, obtusangulo (vel acutangulo) ; semicellulis ellipticis (vel subtri- 

 angularibus), dorso nonnihil convexo, utroque fine in aculeum achroum rectum vel varie cur- 

 vatis productis; a vertice tri angularibus (vel quadrangularibus), angulis saepe rotundatis 

 aculeo interdum obsoleto imposito. 



Diam._Lat. t|§o"— tAW = 0008"-.001". Long. ^5^5/— t^VW = .0008"-. 0001". 

 Syn. — Staurasttrum dejectum, BrSbisson. Rabenhorst, Flora Europ. Algarum, Sect III 

 p. 203. 



