(50) 



flat, till, in large specimens, it is fonr or five feet long, and two or three 

 inches wide, with the margin veiy much waved and curled." — Pliyc. Brit. 

 In full-grown plants the primary root seems to have disappeared, " the 

 collar-like expansion " having become much extended, forming a hollow 

 flattened disc, tlu'owing out small mostly simple rootlets from its under 

 side and edges, which fix themselves to the rock and supply the place of 

 the primary root. Substance subcoriaceous, rather flaccid when fresh. 

 Colour, a greenish olive, darker in the older parts. Fructification : minute 

 spores, collected into sori, mostly in the waved margins of the stem, and 

 occasionally over the lower portion of the fi'ond ; they are oblong or 

 elliptical, arranged vertically, and closely packed together in dense sori, 

 immediately imder the surface of the part in which they originate. 



This species differs considerably in habit from the other species of the 

 genus, but surely not so much as, in a small genus like the present, to 

 render it desirable to form a new one for its reception. The disappear- 

 ance of the first root and the formation of a new one, is a curious and 

 interesting feature in its history, and the flattened, winged stem is a 

 character no less remarkable than peculiar, but the character derived 

 from the fructification is not by any means constant, the sori being 

 frequently scattered over the surface of at least the lower part of the 

 frond, and possibly at times over tlie whole of it, as in the other species 

 of Laminaria. 



The fronds of this species often grow to an immense size ; so large, 

 that when spread out they have been found to " cover a space of twelve 

 feet diameter." 



It is said to be abundant on the British shores, and is given in Don's 

 List of Forfarshire Alga?, but we have not met with it, nor have we 

 heard of its recent occurrence there. 



The formation of a second root is perhaps a provision in this species, 

 rendered necessary by its immense size ; when full grown requiring a 

 much broader and stronger holdfast than the first root could be capable 

 of producing, or at least of producing in sufiicient time for rendering it 

 due suj^port ; the lower part of the stem becoming hardened by age 

 and growing more slowly, some new process is necessary to give it 

 security and strength by fixing the point of support at a higher part 

 of the stem. 



The splitting of the frond in this genus does not seem to be a natural 

 but an artificial pi'ocess, and to be caused by the constant action of 

 the waves ; hence the edges have generally a torn appearance, and the 

 apices of the lacinise are always erose, from the circumstance of the 

 frond being renewed every year from the summit of the stem, where 

 the growth commences, and the old frond often remaining attached 



