148 FRESH-WATER A L G .E OF THE UNITED STATES. 



A. Cytioderma ljeve vel rarissime subtiliter punctatum. 



Cytioderm smooth oh very rarely very finely punctate. 



1. Semicellularum anguli rolundati. 



Angles of the semicells rounded. 



St. ■ntiticiiin, Breb. 



St. a fronte orbiculare, loeve, profunde constrictum, nudum, vel muco plus miuusve firmo invo- 

 lutum ; semicellulis ellipticis, a vertice conspectis 3-4 augularibus (rarius quinquangularibus) 

 angulis rotundatis, lateribus levitcr sinnato-retusis; zygosporis aculeatis, aculeis elongatis, 

 subulatis, furcatim fissis. (R.) Species viihi ignota. 



Z)m»i.— 0.0013"— 00014:". (R.) 



Syn. — S. muticum, Brebisson. Rabenhorst, Flora Europ. Algar., Sect. III. p. 200. 



E^ab. — 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, (Eiirb.) Ralfs. 



St. suborbiculare, Iseve, saepius muco matricali involutum ; semicellulis divcrgentibus, semi, 

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

 minus sinuato-retusis ; zygosporarum aculeis elongatis, subulatis, iutegris. (R.) 



Diam— .002". 



Syn. — St. orbiculare, (Eiirb.) Ralfs, British Desmidiese, p. 125. Rabenhorst, Flora Europ. 

 Algarum, Sect. III. p. 200. 



Hab. — 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 view of a frond of 

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



2. Semicellularum anguli mucronali vel aridati. 



Angles of the semicells mucronate or bristly. 



St. loiigi^piniiiii, (Batley) Archer. 



St. magnum triangulare, Iseve, angulis in aculeos geminos validos subulatos longe productum, 

 lateribus subplanum. (R.) Species viihiignota. 



Syn. — Didymocladon longisjnnum, Bailey, Microscopical Observation.?. 



Hab. — Florida; Bailey. 



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



St. dejectiiin, Brebisson. 



St. lajve, parvura, sinu amplo, obtusangulo (ve! acutangulo) ; semicellulis ellipticis (vel subtri- 

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

 viitis productis; a vertice triangularibus (vel quadrangularibus), angulis sape rotundatis 

 aculeo iiiterdum obsoleto imposito. 



Diam.— Lat. .^1^"— tAitt" = 0008"— .001". Long, t-Vott"— t-Vs/ = .0008"— .0001". 



Syn. — Staurastrum dejectum, Brebisson. Rabenhorst, Flora p]urop. Algarum, Sect. IIL 

 p. 203. 



