90 ACOTYLEDONS. ALG.E. Ulva. 



Div. III. Ujlvoidejj. Fndt: either naked seeds immersed in 

 the frond or capsules. Frond continuous ; its structure cel- 

 lular siibregular. Substance suhmeynhranaceous^ thin. Co- 

 lour frequently greenish. Frond plane or tubular, containing 

 immersed seeds, or capsules of the same substance and colour 

 as the frond, or minute blackish tubercles scattered upon the 

 frond. 



18. ZONARIA. 



Capsules apjiroximated and arranged in linear parallel lines. — 

 Root and stipes downy. Frond membranaceous or subcoria- 

 ceons, llabelliform or dichotomous, composed of straight par- 

 allel fibres from the base to the summit, often interrupted by 

 darkish transverse lines. 



* Lines of fructijication concentrical (Frond flabelliform). 



1. Z. pavonia, frond subcoriaccous flabelliform subdichotonious 

 greenish brown above with numerous concentric lines of fruc- 

 tification, white and somewhat powdery beneath. Ulva pavo- 

 nia, Lightf.p.966. E.B.t. 1276. 



Har. Sea-rocks near Aberdeen, discovered by D. C'argill, above 140 

 years ago, according to Lightf. 



** Lines of fructification interrupted (Frond generally narrow and 

 dichotomous) . 



2. Z. dicliotoma, frond membranaceous olive-green dichoto- 

 mously divided linear obtuse, fructification in longitudinal in- 

 terrupted dots. Ulvadichotoma, Lightf p. 975. t. 34. F.B, 

 t. 774. Hook, in Fl. Lond. with a figure. 



Mab. In basins of water among the rocks, about Leith, New-Haven, 



&c., Liglitf, 

 Frond 3 — 6 inches long, thin and membranous. 



19. ULVA. 



Seeds placed in clusters frequently of four, and scattered through- 

 out every part of the ^'/o/zc?. — Frond membranous or gelati- 

 nous, plane, plicated, or tubular. Mostly marine ; some fevv 

 are inhabitants of fresh water, rarely growing out of water. 

 * Fronds jihine. 



1. U. Lactuca, fronds aggregate oblong plane waved green at- 

 tenuated below spreading upwards and cut and crisped at the 

 margin. Ag.p.AO. Lightf. p. 970. E. B. t. \55l. 



Hab. In the sea, frequent, growing upon stones, shells, &c., Lightf. 



Substance very thin, semipellucid, varying much in size, and I suspect 

 the Ulva latissima of Agardh to be only a var. Fronds clustered. 

 Agardh says they are at first saccate, but soon open at the base, 

 and spread out. This is the " green Laver," or " ovster-green," 

 known at table, where it is served occasiouallv stewed with leniun- 



