60 
ULYACEAE. 
Specimens are often found pierced with holes, the result either of age or of the attacks 
of worms. Such individuals constitute the Phycoseris myriotrema of Kiitzing. 
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. Ay. Sp. Alg. ], p. 409. Grev. Crypt. Scot. t. 313. Harv. 
Phyc. Brit. t. 243. Kiitz. 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 JJ. 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 , Both. ; frond very delicate, gelatinoso-membranaceous, at first 
saccate, afterwards bursting, and opening out into a broad, wavy or torn floating 
membrane. Both, Cat. Bot. 3, p. 329. Ag. Sp. Alg. 1 ,p. 414. Harv. Man. Ed. 1, 
p. 171. Hass. Br. Fr. Wat. Alg. p. 297, t. 78 , Jig. 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 Begions 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 differs by 
any definite character. 
Y. TETBASPOBA. Link. 
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.) 
