150 FRESU-WATER ALGJE OF THE UNITED STATES. 



B. Cytioderma granulatum vel verrucosum. 



Cytioderm granulate or warty. • 



1. Semicellulse a vertice 3-7 mujtilares ; ainjuU jdus minus radialim elongali. 



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



St. iiiarsai'ifaceiiiii, Eurb. 



St. mediocre, granulatum ; semicellulis convergentibus, subfusiformibns, in medio turaidis, 

 utrinque productis, truncatis, a vertice orbicularibus, 5-7 radiatis, radiis obtuse truacatis 

 achrois, hyaliuis, granulato-margaritaceis. (R.) Sxjecies mihi ignota. 



Diam.— 0.00135"— 0.0017". (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 upward.s, rough with pearly granules, outer margin eon- 

 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. dilatatlliii, Ehrb. 



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

 obtusis vel subtruncatis, a vertice 3— 1-5 radiatis, radiis latioribus, truncatis vel rotundatis, 

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



Dwm.— 0.0008"— 0.0011". (R ) 



Var. alternans. 

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

 nantibus cum semicellulfe inferioris. (R.) 



Var. tricorne. 



Semicellulis fusiformibus, nnnnunquam in medio subtumidis, baud raro isthmo distincto con- 

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

 ductis. (R.) 



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



Sijn. — S. aJternans, Brebisson. Var. allernans et tricorne. Rabenhorst, Flora Europ. 

 Algarum, Sect. III. p. 207. 



Remarlis. — Prof. Rabenliovst considers St. altervan.'i 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 olter an opinion. 

 Mr. Archer describes the two species as follows : — 



St. alternans, Breb. 



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. Tj'a,". Br. jx'os"- 



St. tricorne, Breb. 



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

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



