Ser. CHLOROSPERMES. Fam. Rivulariea. 
Prats COXXXIX. 
RIVULARIA ATRA, Rots. 
Gen. Cuan. Frond globose or lobed, fleshy, firm, composed of continuous 
radiating filaments, annulated within, each springing from a spherical 
globule. Rivutarta (of/),—so named by Roth, in allusion to the 
fluviatile habit of some of the first-discovered species. 
Rivouzarta atra; fronds minute, scattered, globose, or hemispherical, firm, 
smooth, glossy black-green; filaments dark green, densely packed. 
Rivuraria atra, Roth, Cat. Bot. vol. ii. p. 340. Ag. Syn. p.130. Ag. Syst. 
p. 24. #. Bot. t.1798. Harv. in Hook. Br. Fi. vol. ii. p. 392. Harv. 
in Mack. Fl. Hib. part 3. p. 235. Harv. Man. p. 152. 
Evactis atra, Kitz. Phyc. Gen. p. 241. 
Lincxta atra, Zyngb. Hyd. Dan. p. 195. t. 65. 
Livcx1A hemispherica, Schwm. Enum. vol. i. p. 114. 
TREMELLA hemispherica, Linn. Syst. Nat. vol. ii. p. 714. Huds. Fl. Ang. 
p- 565. Lightf. p.900. With. vol. iv. p. 81. 
Cu#topHora atra, 4g. Disp. p. 43. 
Has. On rocks and stones, and on Corallines and other Alge, between 
tide marks. Perennial? At all seasons. Very abundant. 
GroeRr. Distr. Shores of Europe. 
Descr. Fronds one or two lines in diameter, hemispherical when attached to 
flat surfaces, globose when growing on filiform Alga, very hard, of an ex- 
ceedingly firm, compact substance, and dark colour. F/aments subulate, 
attenuated, connected together in branching, subdichotomous series, filled 
with dark-green endochrome, which is annularly divided in the upper part, 
and coheres in oblong masses in the lower. Each filament springs from a 
transparent globule (or connecting cell). 
A very common plant on all rocky shores, growing either on 
the rocks, or on the smaller Algz, especially on Cladophora 
rupestris and Corallina offcinalis. It forms small, hard wart- 
like balls or hemispheres, rarely as large as the seed of Sweet- 
Pea (Lathyrus odoratus), and sometimes completely covers the 
plant to which it attaches itself. 
Carmichael describes an allied species, 2. applanata, said to 
differ from £. ara in being flatter and thinner in substance, and 
growing in similar localities. This I have never seen. 
VOL. Il. Aare! 
