Protococcus.] ALG^E CHLOROSPERMEvE. 245 



sub-orbicular; granules elliptical. Grev. Crypt FL t. 243. /. 2. 

 Harv. in. Hook. Br. FL v. ii. p. 396. 



In heathy places, in moist situations. 



4. P. hyalina, Lyngb. Green pellucid Palmella. Frond 

 globose or somewhat elongated, pellucid green, the granules 

 globose, green. Grev. Grev. Crypt. FL t. 247. Harv. in 

 Hook. Br. FL v. ii. p. 397. 



In fresh water streams, &c. 



82. NOSTOC. Vauch. Nostoc. 



Frond gelatinous, or coriaceous, lobed, hollow, or solid ; filled 

 with crisped, momllform filaments, which are finally dissolved 

 into sporules. Name, of unexplained meaning. This genus 

 differs from Palmetto,, solely in the filamentous arrangement 

 of the sporules. To Berkeley's genus Monormia (Gr. Alg. 

 p. 46. t. 18. ) it is still more closely allied, but appears suffi- 

 ciently distinct. 



1. Olive-green, terrestrial. 



1. N. commune, Vauch. Common Nostoc. Terrestrial ; 

 frond expanded, polymorphous, plicato-undulate green. Harv. 

 in Hook. Br. FL v. ii. p. 398. TremelLa Nostoc, E. Bot. t.4Ql. 



Gravelly soils, among rocks, &c. after rain. 



2. N. foliaceum, Ag. Leafy Nostoc. Csespitose, membra- 

 naceous, plicato-rugose, somewhat erect. Ag. Syst. p. 19. 

 Harv. in Hook. Br. FL v. ii. p. 399. 



On clayey, moist ground. 



3. N. microscopicum, Carm. Minute Nostoc. Fronds densely 

 aggregated, very minute, polymorphous, immersed in a blackish 

 crust. Harv. in Hook. Br. FL v. ii. p. 399. 



On rocks, and among mosses. At the " Wilderness," Clonmel. 

 Fronds exceedingly minute, hyaline or pale olive, of various shapes, 

 containing- a few, lax, moniliform filaments. 



2. Olive-green, submersed. 



4. N. verrucosum, Vauch. Plaited Nostoc. Fronds large, 

 gregarious, confluent, subglobose, plaited, at length hollow, 

 blackish green. Harv. in Hook. Br. FL v. ii. p. 400. 



On stones in alpine rivulets. 



83. PROTOCOCCUS. Ag. Protococcus. 

 Plant consisting of aggregated, naked globules, filled with mi* 



