OSCILLATORIA. 255 



that of O. mtisconim, than which, however, it is much more 

 tough and elastic : the filaments likewise are much smaller. 

 They are intermediate in diameter between those of O. sub- 

 fusca, and O. violacea, differing also from both in some other 

 respects. They are more brittle than those of O. suhfusca, 

 though like those of that species they preserve their diameter 

 in drying, which is not the case with O. violacea. The striae 

 are close, and tolerably evident. 



18. OSCILLATORIA SPADICEA Carm. 



Plate LXXI. Fig. 5. and Plate LXXIL Fig. 5. 



Char. Stratum very thin, spreading. Filaments yellowish 

 brown, thick, variously curved and twisted. Strige con- 

 spicuous, and very close. 



O, spadicea Harv. Hook. Brit. Fl. p. 378. ; Harv. in 

 Manual, p. 167. 



Hob. On damp mossy earth ; rare. Appin : Capt. Carmi- 

 chael, Ireland : Mr. Moore. Cheshunt : A. H. H. 



" It occurs in a very thin dark green stratum, spreading to 

 the extent of several feet, and is hardly to be distinguished 

 from the mossy earth on which it grows. Filaments short, 

 straight, curved, or spirally twisted, radiating in all directions, 

 and possessed of all the movements peculiar to the tribe." — 

 Carm. 



c. Stratum blackish ; filaments brittle, not coriaceous, 

 19. OSCILLATORIA NIGRA Vauch. 



Plate LXXI. Fig. 3. 



Char. Stratum black ; when dry bluish black, with long radii. 

 Filaments pale bluish green, thick. Striae very distinct 

 and close. 



Hook. Scot. ii. p. 79. Conf. fontinalis Dillw. t. 64. 

 O, limosa, Grev. Edin. p. 303. O. nigra Harv. in 

 Manual, p. 165. 



