92 CONFERVACE^ 



Confervoid Algaj, forming decumbent strata ; the filaments lying heaped together, 

 and emitting at irregular distances rootlike branches. Kiitzing enumerates 28 species, 

 among which are several which we refer to Choetomorpha. 



1. Rhizoclonium riparium, Roth. ; filaments long, slender, decumbent, pale-green, 

 forming wide strata, flaccid, entangled, angularly bent, furnished at the angles with 

 short, rootlike processes (which sometimes, but rarely, lengthen into very patent 

 branches, and often attach themselves to neighbouring filaments). Conf. riparia, Roth. 

 Cat. Bot. 3.J9. 216. E. Bot. t. 2100. Dillw. Conf. p. 111. Sup. t. E. Ag. Syst. 

 p. 106. Harv. Phyc. Brit. t. 238. Conf. obtusangula, Lyngb. Hyd. Dan. t. 55. B. 

 Rhizoclonium obtusangulum, Kiitz. Sp. Alg. ^.261. 



Hab. On sand covered rocks near high water mark. Greenland, Wormskiold, fide 

 Lyngbye. (v. s.) 



I have not seen American specimens of this plant. 



Order YII. ZYGNEMACE^. 



Zygnemacece, Kiitz. Phyc. Gen. p. 274. Sp. Alg. p. 433. Zygneniece, Endl. 3d 

 Suppl. p. 14. Algce Synsporeoe^ Dne. Class, p. 32. Conjugates, Berk. Crypt. Bot. 

 p. 150. Conjugatece, Hass. Br. Fr. W. Alg., p. 129. 



Diagnosis. Green (freshwater) Algae, consisting of simple, articulated, floating 

 threads, composed of cylindrical, seriated cells. Endochrome usually definitely figured. 

 Spores of large size, and mostly solitary, formed by the union of two endochromes or 

 by the division of a single endochrome. 



Natural Character. Freshwater, floating, confervoid Algae, at first consisting of 

 unbranched threads, formed of a number of cylindrical cells placed end to end ; after- 

 wards often linked together in pairs by connecting processes. The endochrome in 

 different genera puts on a variety of forms. It is rarely diffused equally through 

 the cell as in ordinary Confervae, but is either arranged in spiral bauds, attached to 

 the cell-walls, or divided into two star-like masses ; or it consists of larger and smaller 

 grains subsymmetrically arranged. The cell-wall varies also much in character ; in 

 some it is membranous, in others gelatinous, and occasionally very thick. The 

 fructification consists of large and mostly solitary spores formed usually from the union 

 and condensation of the contents of two cells, either consecutive cells of the same fila- 



