126 FRESIl-WATER AhGM OF THE UNITED STATES. 



Genus DESMIDIUM. 



CellultD obloiigo-tabulares, medio inciso-bilobae, lobis iiitegris vel irregulariter dentatis, a fronte 

 tri- vel quadrangulares, aiigulis obtuse rotuudatis, in fila angulosa, proelonga, torta, fragiles arete 

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

 duabus lateralibus divergeutibus compositus. Zygospore globose vel oblonga;, glabrae. 



Cells oblong-tabular, mcdianly incisely bilobate, with the lobes entire or irregularly dentate, aa 

 seen from tliu 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. 



D. Swarlzii, Ao. 



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



Dmm.— 0.00096"— 0.00189". (R.) 



Si/n. D. Sv:artzii, Agardii. Rabeniiorst, Flora Europ. Algarura, Sect. III. p. 154. 



Uab. In iiquis quietis, Atlantic States. Florida; Georgia; South Carolina ; Rhode Island; 



Railey. Kew 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 ; .eudochrome three-rayed. Archer. Pritchard's /h/u- 

 sona. 

 D. qiiadrangulaf iiin, Ktz. 



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

 formibus obtusis, a fronte sinuato-quadrangularibus, augulis late rotuudatis, lateralibus exca- 

 vatis. (R.) Species mihi ignota. 



X»iam.— 0.0021"— 0.0029". 



Syn. — D. quadrangulatum, Kutzinq. 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; eudochrome four 

 rayed. L. ^.\^". B. ^J,"-,!^". (Archer) 



D. aptogoniuin, Breb. 



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

 lateralibus concavis, lobis crenatis, a fronte triangularibus (nonnunquain biangularibus), centre 

 concavo, angulis rotuudatis protensis isthmum brevissimum triplicem effieientibus. (R.) 

 Species niihi ignota. 



Dmm.— 0.00089"— 0.001 47". (R.) 



Syn. — Aptogomiim desmidium, Ralfs, British Desmids. 



D. aidogonium, Brebisson. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 155. 



HaJ). — Georgia ; South Carolina ; Bailey. 



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

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

 ducing intervening central oval foramina. Archer. 



Genus APTOGONIUM, Ralfs. 



Cclluhe 3-4 angulares vel compressse, non constrietae ; uiargiue laterali plana; vel crenatse, ip 

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



