24 RHODOMELACEiE. y. 



associated together by a common habit, but it is not easy to point out a clear generic 

 character which will separate them from Rytiphkea and from the more opaque species 

 of Polysiphonia, from which genera they chiefly differ in their denser cellular sub- 

 stance and the absence of all appearance of articulation iu any part, even the young- 

 est, of the frond. In a young state, or when the frond is in active extension, the 

 apices of the branches are clothed with dichotomous fibrils, resembling in structure, 

 and no doubt analogous to, the ramelli of Dasya ; but these fibrils are fugacious, as 

 in Poli/siphonia, &c. 



Of the North American species, three belong to the Pacific, and three to the 

 Atlantic Coast. 



1. RiiODOMELA Larix, Ag. ; frond robust, terete, alternately branched; branches 

 long, subsimple, densely clothed with quaquaversal, tufted, inflexed, subulate 

 ramuli; stichidia attenuate, among the clustered ramuli. Ag. sp. Alg. I, p. 376. 

 Lophura Larix, Kiitz. Sp. Alg. p. 850. Fucus Larix, Turn. Hist. tab. 207. 



Hab. Pacific Coast from the shores of the Arctic Sea (Seeinan) to Monterey, 

 abundantly. Coulter! Tolmiel Wilkes/ Garry! &c. Discovered at Nootka Sound 

 by A. Menzies, Esq. (v. s. in Herb. T. C. D.) 



Frond G-14 inches long or more, terete, the thickness of a crowquill, undivided 

 to the height of two or three inches, thence upwards much branched. Branches 

 alternate, 4-6 inches long, simple, or bearing in the upper half several secondary 

 branches, and, occasionally, in luxuriant specimens, a third set. The lower part of 

 the stem is commonly bare, or clothed with the broken stumps of old branches, but 

 all the younger parts of the frond are densely covered on all sides with spirally 

 disposed tufts of short, inflexed, subulate ramuli, two or three lines in length. 

 These ramuli spi-ing from very short or abortive lateral branchlets on which they 

 are inserted one above the other, but so near together as to appear foscicled. Some- 

 times the axis of the fascicle is a little lengthened and then the ramuli appear 

 scattered, but are still very closely placed. Judging from dried specimens the 

 ramuli are laterally compressed, shaped like the blade of a knife. The false 

 stichidia are formed from the inner or upper ramuli of the fascicles, and are gener- 

 ally found on such specimens as have the axis of the fascicles a little lengthened. 

 They are more slender than ordinary ramuli, and of greater length, but scarcely 

 less opaque: the tetraspores are small. Conceptacles ovate, crowding at the base of 

 the tufted ramuli, being formed from the inner ones of the fascicles. Substance 

 coarse, between coriaceous and cartilaginous. In drying the plant becomes almost 

 black, and does not adhere to paper. 



2. Rhodomela floccosa, Ag. ; stem filiform below, compressed above, alternately 

 branched ; branches spreading, subsimple, pinnated throughout with short, alter- 

 nate, distichous, fasciculato-multifid, compressed ramuli ; stichidia lanceolate, formed 



