ULVA. 297 



scattered through the frond either singly, in pairs, or in 

 fours. 

 Name supposed to be from ul, water, in Celtic. 



1. ULVA BULLOSA Roth. 

 Plate LXXVIII. Fig. 13. 



Char. Frond very delicate, somewhat gelatinous, at first sac- 

 cate, afterwards becoming expanded into a broad waved 

 or torn floating membrane. 



Eng. Bot. t. 2320.; Hook. Brit. Flor. vol. ii. p. 312.; Harv. 



in Manual, p. 171. 

 Hob. In stagnant freshwater ponds and ditches. 



Fronds clustered, at first fixed, afterwards floating, very thin 

 and gelatinous, of a pale green colour, becoming yellowish. 

 Cells in the fully developed plant single, and equally diffused 

 throughout the lamina. If this disposition of the cells be not 

 constant, and if in the young condition of the frond they are 

 ever arranged in fours, as I believe to be the case, then I think 

 that this species can scarcely be regarded as distinct from 

 Tetraspora lubrica. The size of the cells is the same in both. 



2. ULVA CRiSPA Light. 

 Plate LXXVIII. Fig. 12. 



Char. Fronds terrestrial, saccate, firm, densely tufted, 



plaited and wrinkled, of a roundish form. Cells arranged 



in fours, crowded. 

 Ulva crispa Lightfoot. Grev. Alg. Brit. p. 175.; Hook. 



Brit. Flor. vol. ii. p. 312. ; Harvey, in Manual, p. 171. 



Ulva furfuracea Horncastle. Grev. Crypt, t. 265. ; 



Hook. Brit. Flor. p. 312. ; Harvey, in Manual, p. 171. ; 



E. B. t. 2754. 



Hob. On damp ground, rocks, thatched roofs , &c. ; very 

 common, winter and spring ; rocks near the sea : Appin : 

 Captain Carmichael. On the walls of King's College, 

 Cambridge: Rev. M. J. Berkeley. Several places near 



