126 FRESH-WATER ALG^E OF THE UNITED STATES. 



Genus DESMIDIUM. 



Cellulae oblongo-tabulares, medio inciso-bilobae, lobis integris vel irregulariter dentatis, a fronte 

 tri- vel quadrangulares, angulis obtuse rotundatis, in fila angulosa, praglonga, torta, fragiles arete 

 connex*. Massa ehloropbyllosa (a cellulse fronte visa) 3-4 radiata ; quisque radius e lamiuis 

 duabus lateralibus divergentibus compositus. Zygosporae globosa? vel oblongae, glabrje. 



Cells oblong-tabular, medianly incisely bilobate, with the lobes entire or irregularly dentate, as 

 seen from the front tri- or quadrangular, and having the angles obtusely rounded, closely conjoined 

 into an angular, fragile, twisted filament. Chlorophyl (as seen from the front) 3-4 radiate ; each 

 radius composed of two lateral divergent lamina ; zygospores globose or oblong, smooth. 



I>. Swartzii, Ao. 



D. cellulis a fronte triangularibus, diametro 2-3 plo brevioribus. (R.) 



Diam. 0.00096" 0.00189". (R.) 



Syn. D. Sivartzii, AGARDH. RABENHORST, Flora Europ. Algarum, Sect. III. p. 154. 



Eab. In aquis quietis, Atlantic States. Florida; Georgia; South Carolina ; Rhode Island ; 

 Bailey. New York; Edwards. Pennsylvania ; Wood. 



Filament triangular, equal, with a single longitudinal waved, dark line, formed by the third 

 angle; joints in front view somewhat quadrangular, broader than long, with two slightly 

 angular crenatures on each lateral margin, united at the whole of their end margins by a 

 thickened border, end view triangular; endochrome three-rayed. Archer. Pritchard's Infu- 

 soria. 



D. quadrangnlatum, KTZ. 



D. quadrangulare, cellulis oblongo-quadrangularibus, diametro 2-3 plo brevioribus, lobis denti- 

 formibus obtusis, a fronte sinuato-quadrangularibus, angulis late rotundatis, lateralibus exca- 

 vatis. (R.) Species mihi ignota. 



Diam. 0.0021" 0.0029". 



Syn. D. quadrangulatum, KUTZINQ. RABENHORST, Flora Europ. Algarnm, Sect. Ill, p. 155. 



Filament quadrangular, varying in breadth from its twisting, having two longitudinal waved 

 lines ; joints in f. v. broader than long, with two somewhat rounded crenatures on each lateral 

 margin, united by the whole of their end margins ; e. v. quadrangular ; endochrome four 

 rayed. L. T5 4? ". B. ri"-*h" (Archer) 



D. aptogo ilium, BREB. 



D. fasciis plerumque subbrevibns, nudis, perforatis; cellulis quadrangularibns, inciso-bilobis, 

 lateralibus concavis, lobis crenatis, a fronte triangularibus (nonnunquam biangularibus), ceutro 

 concavo, angulis rotundatis protensis isthmum brevissimum triplicem efficientibus. (R.) 

 Species mihi ignota. 



Diam. 0.00089" 0.00147". (R.) 



Syn. Aptogonium desmidiwm, RALPS, British Desmids. 



D. aptogonium, BREBISSON. RABENHORST, Flora Europ. Algarum, Sect. III. p. 155. 



Hob. Georgia; South Carolina; Bailey. 



Joints in f. v. quadrangular, broader than long, with two rounded crenatures on each lateral 

 margin, united at the outer portion only of each end margin by mutual projections, thus pro- 

 ducing intervening central oval foramina. Archer. 



Genus APTOGONIUM, RALFS. 



Cellulse 3-4 angnlares vel compressse, non constrictee ; margine lateral! plants vel crenatse, io 

 fascias peiforato-articulatas, angulares conjunctae. (R.) 



