126 FRESH-WATER ALG^ OF THE UNITED STATES. 



Genus DESMIDIUM. 



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

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

 connexai. Massa chlorophyllosa (a cellulae fronte visa) 3-4 radiata ; quisque radius e laminis 

 duabus lateralibus divergentibus eompositus. Zygosporae globosae vel oblongs, glabrae. 



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. 



1>. Swartzii, A». 



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



Drnrn.— 0.00096"— 0.00189". (R.) 



Syn. D. Sivartzii, Agaedh. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 154. 



ffab. 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. qnadrangnlatnm, 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. 



Zhfflm.— 0.0021"— 0.0029". 



Syn. — D. quadrangulatum, Kxttzing. Rabenhorst, Flora Europ. Algarum, 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. ^^\:,". B. ^hi"—^h"- (Archer) 



D. aptog^oninm, Bb£b. 



D. fasciis plerumque subbrevibus, nudis, perforatis; cellulis quadrangularibus, inciso-bilobis, 

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

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

 Species mihi ignota. 



Z>iam.— 0.00089"— 0.00147". (R.) 



Syn. — Aptogonium desmidium, Ralps, British Desmids. 



JD. aptogonium, Brebisson. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 155. 



MaJ). — 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, Ealps. 



Cellulse 3-4 angulares vel compressae, non constrictae ; margine lateral! planse vel crenatae, in 

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



