354 < THE SEA SHORE 



cylindrical fronds, which are forked and covered with short hairs 

 that give it a woolly appearance when in the water. Each frond is 

 composed of slender interwoven fibres with club-shaped filaments 

 passing vertically to the surface. It grows on rocks in the pools 

 between the tide-marks, and is abundant on nearly all our coasts. 



The Purse Codium (C. bursa) has spongy hollow fronds of a 

 globular form, varying from a quarter of an inch to five or six inches 

 in diameter. It is a rare species, being found only at a few places on 

 the south coast. Another species (C. adhcerens) adheres to rocks, 

 over which the fronds spread in irregular soft patches, the club- 

 shaped vertical filaments of its interwoven fibres giving it the 

 appearance of rich green velvet. 



An allied weed (Bryopsis), named from its moss-like appearance, 

 grows in erect tufts, each frond consisting of a branched one-celled 

 filament. There are two species of the genus, one (B. plumosa) 

 characterised by the light feathery nature of its fronds, the stems of 

 which are branched only near the top. It is found in rock pools 

 on most of our coasts. The other (B. hypnoides) is more freely 

 branched, and the branches are long, and issue from all sides of the 

 stem. Like the last species, it has branches on the outer part of 

 the stem only, but it is of a softer texture. 



The best known of the green-spored weeds are certainly those 

 belonging to the Ulvacece, characterised by their flat or tubular 

 fronds, sometimes of a purplish colour, the cells of which multiply 

 both horizontally and vertically as the plants grow. In the 

 typical genus, Ulva, the frond is sometimes in two distinct layers, 

 and becomes more or less inflated by the accumulation of either 

 water or oxygen between them. The commonest species are 

 U. lactuca and U. latissima, both of which are eaten by the 

 dwellers on some of our coasts. The former, commonly known as 

 the Lettuce Ulva, has a frond of a single layer of cells, and grows 

 on rocks and weeds between the tide-marks. It is common on many 

 oyster beds, and is employed by the fishermen to cover the oysters 

 when sent to market ; they call it ' oyster green.' This species is 

 shown on Plate VIII. 7. latissima or the Broad Ulva sometimes 

 reaches a length of two feet, and a breadth of nearly a foot. The 

 fronds are composed of two layers of cells, are of an irregular 

 shape, with a very wavy, broken margin, and of a bluish-green 

 colour, It is known as the Green Laver, and is used as food in 

 districts where the true laver (Porphyra) is not to be obtained. A 

 third species the Narrow Ulva (U. Linza) has smaller and 



