Viva.] ALQM CHLOROSPERMEjE. 243 



3. U. Linza, Linn. Ribband green Laver. Frond linear- 

 lanceolate, acute, undulate at the margin, composed of two 

 membranes closely applied. Harv. in Hook. Br. Fl. v. ii. 

 />. 311. 



Rocks and stones in the sea. The double membrane of this species 

 closely allies it to the genus Enteromorpha ; from which, indeed, it 

 rather differs in habit than by any distinct character. 



* * Found in fresh toater. 



4. U. bullosa, Roth. Blistered Ulva. Frond very delicate, 

 somewhat gelatinous, at first saccate, afterwards becoming ex- 

 panded into a broad, waved or torn floating membrane. Hook. 

 Br. Fl. v. ii. p. 312. E. Bot. t. 2320. 



In stagnant fresh-water pools and ditches. This species scarcely 

 differs in its frond and fructification from Tetraspora, and, indeed, 

 there are some varieties very difficult to be distinguished from T. 

 lubrica. Dr. Hooker hints, that it may be only U. Lactuca, altered 

 by growing in fresh water. It is impossible to say whether or not this 

 opinion be correct, for in plants of such low organization, when place 

 of growth constitutes a specific character, the difference between 

 species and varieties is often so vague, that we are forced, in many 

 cases, to rest content with a random guess. 



* * Grow on damp ground, walls, rocks, paling, S)-c. 



5. U. crispa, Lightf. Crisped Ulva. Fronds saccate, firm, 

 densely caespitose, plaited and wrinkled, of a roundish form. 

 Hook. Br. Fl. v.u.p. 312. 



On damp walls, the thatched roofs of cottages, &c. very common. 



6. U. calophylla, Spreng. Beautiful Ulva. Fronds densely 

 caespitose, plane, lineari-ligulate, attenuated at base (often sti- 

 pitate), longitudinally striate, each striae marked with a series 

 of bi-quaternate granules. Hook. Br. Fl. v. ii. p. 312. — Bangia 

 calophylla, Carm. in Grev. Crypt, t. 220. 



On damp stones, walls, &c. On a damp window-stone in the City 

 of Limerick, gathered in abundance in the month of February ; W. 

 H. Harvey. A highly beautiful and curious plant. Frond 8 — 4 lines 

 long, rising from a filiform, cylindrical, (?) often elongated stipes, from 

 which it suddenly expands into a strap-shaped or narrow oblong mem- 

 brane. Dr. Greville does not notice this stipes, except in calling the 

 fronds " attenuated at the base." In many instances I allow they are 

 gradually attenuated, but in others I have distinctly seen them sud- 

 denly expand from a filiform and apparently cylindrical stem, which is 

 transversely fasciate, and, indeed, strongly resembles the filament of 

 Lyngbya speciosa. If this stem be truly cylindrical, U. calophylla 

 is brought still closer to U. velutina. I may also remark, without 

 wishing to favour the opinion, that the supposed transmigration of this 

 species into Lyngbya muralis, (which Agardh ridicules in the second 

 vol. of his Species Algarum, Introcl. p. xlv.) may be accounted ior 



