216 ULVA. PORPHYKA. 



II. ULVA. Linn. [Plate 25, B.] 



Frond meinbranaceous, of a green colour, plane, (in some 

 cases saccate, and inflated in the young state). Fructifica- 

 tion: minute granules, mostly arranged in fours. Name, 

 supposed to be from Ul, water in Celtic. 



1. U. latissima, Linn. ; frond broadly-ovate or oblong, 

 flat, delicately membranaceous, of a full green colour. Grev. 

 Alg. Brit. p. Ml', Hook. L c. p. 311 ; IVyatt, Ala. Danm. 

 No. 33. U. Lactuca, E. Bot. t. 1551. 



In the sea, on rocks, stones, &c., very common. Annual. All the year 

 round. Fronds tufted, 6 18 inches long or more, and several inches wide, 

 variously waved and lobed. Fructification covering the whole frond. 



2. U. Lactuca, Linn. ; frond at first obovate, saccate, 

 inflated, at length cleft down to the base, the segments plane, 

 unequal, laciniated, semi-transparent. Grev. Hook. 1. c. p. 

 311 ; Grev. Crypt. Fl. #.313. 



On rocks, stones, corallines, &c. in the sea. Annual. May and June. 

 " Fronds 3 6 inches in length, in the young state obovate and saccate, 

 but very soon bursting and lacerating, at length cleft irregularly to the 

 base.'' Grev. A smaller and far more tender plant than the preceding, and 

 of a pale yellow-green colour. It adheres closely to paper in drying. 



3. U. Linza, Linn. ; frond linear-lanceolate, acute, undu- 

 late at the margin, composed of two membranes closely 

 applied. Hook. I. c.p. 311 ; Wyatt, Alg. Danm. No. 164. 



Rocks and stones in the sea. Annual. Summer. Fronds clustered, 6 

 inches to 2 feet in length, half an inch to an inch and a half wide, linear- 

 lanceolate, tapering to each extremity, much curled, of a fine grass-green 

 colour. This species, as Dr. Greville observes, shows by its double mem- 

 brane a transition to Enteromorpha. 



III. PORPHYRA. Ag. [Plate 25, A.] 



Frond plane, exceedingly thin, and (owing to the fructifi- 

 cation) of a purple colour. Fructification: 1, scattered 

 sort of oval seeds ; 2, roundish granules, mostly arranged in 

 a quaternate manner, and covering the whole frond. Grev. 

 Name, xofxpupog, purple. 



1. P. laciniata, Lightf.; fronds deeply and irregularly 

 cleft, with broad segments ; margin variously cut and lobed. 

 Grev. Alg. Brit. p. 168 ; Hook. Br. Fl. ii. p. 310 ; Hare. 



