150 FRESH-WATER ALG^ OF THE UNITED STATES. 



B. CtTIODEEMA GEANUIiATUM VEL VERRUCOSUM. 



Cytioderm granulate or warty. 

 1. Semicellulee a vertice 3-1 angulares; anguli plus minus radiatim elongatl 



Semicells seen from the vertex 3-7 angled; angles more or less radiately produced. 



St. margaritacenni, Ehrb. 



St. mediocre, granulatum ; semicellulis convergentibus, subfusiformibus, in medio tumidis, 

 utrinque productis, truncatis, a vertice orbicularibus, 5-T radiatis, radiis obtuse truncatis 

 aclirois, hyalinis, granulato-margaritaceis. (R.) Species mihi ignota. 



Diam.— 0.00135"— O.OOn". (R.) 



Syn.—St. margaritaceum, (Ehrb.) Menegheni. Rabenhorst, Flora Europ. Algarum, Sect. 

 III. p. 206. 



Eab. South Carolina ; Georgia ; Florida ; Rhode Island ; Bailey. 



Segments in f. v. gradually widening upwards, rough with pearly granules, outer margin con- 

 vex, produced at each side into a colorless, more or less attenuate, short process, having the 

 granules in transverse lines, blunt and entire at the apex, e. v. circular, bordered by from five 

 to seven short, narrow, obtuse, colorless, granulate marginal rays. (Archer.) 



St. dilatatum, Ehrb. 



St. parvum, granulatum ; semicellulis rectis, cylindrico-fusiformibus, non tumidis, utroque fine 

 obtusis vel subtruncatis, a vertice 3-4-5 radiatis, radiis latioribus, truncatis vel rotundatis, 

 achrois, hyalinis, granulato-margaritaceis. (R.) Species mihi ignota. 



Dmm.— 0.0008"— 0.0011". (R ) 



Var. alternans. 

 Semicellulis ellipticis rectis, utroque fine rotundatis, a vertice triradiatis, radiis obtusis, alter- 

 nantibus cum semicellulee inferioris. (R.) 



Var. tricorne. 

 Semicellulis fusiformibus, nonnunquam in medio subtumidis, hand raro isthmo distincto con- 

 junctis, a vertice 3-4 angularibus, angulis truncatis vel obtusis, plus minus radiatim pro- 

 ductis. (R.) 



Hab. — Georgia; Florida; Rhode Island; Bailey. 



Syn. — iS. alternans, BRfiBissoN. Var. alternans et tricorne. Rabenhorst, Flora Europ. 

 Algarum, Sect. III. p. 207. 



Bemarks. — Prof. Rabenhorst considers St. alternans and tricorne, as simple varie- 

 ties of St. dilatatum, whilst both Archer and Ralfs describe them as distinct. I 

 have not seen either of them, and am not therefore entitled to offer an opinion. 

 Mr. Archer describes the two species as follows : — 



St. alternans, BrIb. 



Segments in front view elliptic or oblong, two or three times as broad as long, separated by a 

 wide sinus, twisted, unequal; rough with very minute pearly granules; e. v. with three 

 obtuse and rounded angles, forming short, not colorless rays, alternating with those of the 

 other segments, sides concave. L. xttst"- Br. xiVff"- 



St. tricorne, BRiB. 



Segments in f v. somewhat fusiform, often twisted, rough with minute puncta-like granules, 

 tapering at each side into a short, usually colorless process, blunt or divided at the apex ; 



