60 ULVACEiE. 



Specimens are often found pierced with holes, the resiilt either of age or of the attacks 

 of worms. Such individuals constitute the Phycoseris myriotrema of Kiitziug. 



Sect. 2. Ulva. Membrane formed of a single layer of cellules. 



4. Ulva lactuca, Linn. ; " frond at first obovate, saccate, inflated, at length cleft 

 down to the base ; the segments plane, unequal, laciniated, semi-transparent," Grev. 

 Lin.Sp. PL p. 1632. Ag. Sp. Alg. 1, p. 409. Grev. Crypt. Scot. t. 313. Harv. 

 Phyc. Brit. t. 243. KUtz. Sp. Alg. p. 474. 



Hab. Boston Bay, Miss E. H. Brewer. Indianola, Texas, Dr. Schott. (v. v.) 



Much thinner and more delicate in substance, and of a paler colour than U. latissima ; 

 and clearly characterised, on dissection, by its simpler membrane. It is more trans- 

 parent, and the cells are more regularly grouped in fours, more distant, with hyaline 

 interspaces. When young it forms a bag, like a very short and broad Enteromorpha. 

 It closely adheres to paper in drying. 



5. Ulva bullosa, Roth. ; frond very delicate, gelatinoso-membranaceous, at first 

 saccate, afterwards bursting, and opening out into a broad, wavy or torn floating 

 membrane. Roth, Cat. Bot. 3,|>. 329. Ag. Sp. Alg. l,p. 414. Harv. Man. Ed. 1, 

 p. 171. Hass. Br. Fr. Wat. Alg. p. 297, t. 78, fig. 13. Tetraspora bullosa, Kiitz. 

 Sp. Alg. p. 226. 



Hab. In fresh-water ponds and ditches. Whalefish Islands, Davis's Straits, Dr. 

 Lyall. (v. V.) 



Probably as common in stagnant pools in America as it is in Europe, but I have as 

 yet only seen specimens brought from the Arctic Regions by Dr. Lyall. When young 

 it is attached, and somewhat tubular, like large specimens of Ent. intestinalis ; but it 

 afterwards bursts open, and then generally floats on the surface, being buoyed up by 

 bubbles of oxygen, which it disengages. 



By Kiitzing this species is referred to Tetraspora, from which it scarcely difiers by 

 any definite character. 



V. TETRASPORA. Li7ih 



Frond gelatinoso-membranaceous, tubular, inflated or flat, green. Fructification, 

 green granules (spores) arranged in fours, dispersed throughout the hyaline cells of 

 the frond. (In fresh water.) 



