22 BYHOP8I8 OF BRITISH sr. vweeds. 



lesser details of it > habit, there is bo much difference in the 



relative breadth of the frond, that specimens from diff 

 parts of the coast have a very opposite aspect. In 



the branches arc broader than our Larger i'._ 

 and these approach the narrower forms of the ex< 

 herbacea, whose broader varieties have branches as wide as 

 the laciniae of a Laminaria; in others the frond is so nar- 

 row, that, as Mr. Turner well observes, such individuals 

 may. at first Bight, be mistaken for luxuriant fronds of D. 

 viridus, whose narrower varieties are as delicate as the 

 finest Conferva 1 . D. Ugulata is widely distributed in the 

 Northern Atlantic, and probably as common on the Ame- 

 rican as the European side, though we have as yet no evi- 

 dence of the fact. Iii the southern hemisphere I am only 

 aware of its having been found at Cape Horn, where Pr. 

 J. D. Hooker dredged specimens from a considerable 

 depth. 



18. aculeata {The prickly Desmarestia) ; stem short, cylindri- 



cal, bearing numerous slender, elongate, flattish, irregularly 

 bi-tri-pinnate branches ; pinnae and pinnula? alternate, taper- 

 ing at the base, filiform, either fringed with opposite tufts 

 of bright green fibres, or margined with erect, awl-shaped, 

 alternate, distichous spines, Lam. Ess. p. 25. (Atlas, PI. V. 

 Fig. 18.) 

 Desmia aculeata, Lyngb. Sporoehnus aculeatus, Ag. Fucus acu- 



leatus, Linn. F. museoides, Linn. 

 JSab. On rocks and stones in the sea, near low-water mark, and 

 at a greater depth. Perennial. Common on the shores of 

 the British Islands. 

 At different stages of its growth this plant presents such 

 opposite appearances, that a young botanist may readily 

 mistake for two species, forms which depend entirely .on 

 age, and which have deceived even Linnaeus himself. When 

 young, the whole frond is of a tender substance, bright- 

 green colour, and beautifully fringed with filaments; when 

 old, it is coarse, brown, naked, and thorny. In plants of 

 the second year, such as our figure represents, these cha- 

 racters are often found combined in the same specimen, in 

 which the older parts of the frond are naked and spiny, the 

 younger shoots being green and clothed with pencilled fila- 

 ments. No fructification has yet been observed on this or 

 any other species of Desmarestia. 



19. viridis. {The green Desmarestia) ; frond cylindrical, filiform, 



