Both branchlets and ramuli are marked with dark, transverse lines, or 
spurious articulations, at short intervals, an appearance caused by the arti- 
culated, polysiphonous axis of the frond being seen through the subtrans- 
parent cells of the periphery. Fructification ; 1, ceramidia ovate, on longish 
pedicels, borne along the inner faces of the secund ramuli, 2, Stichidia, which 
occupy a similar position on distinct plants, and are shortly stalked, lanceo- 
late, and uncinate. Te¢raspores triangularly parted. Substance cartilaginous 
and tough; very rigid when dry, and not adhering to paper. Colour a 
dark, dull red, becoming black in dying. 
ree 
This is one of those plants which, abundant along the shores 
of southern Europe, reaches its northern limit on the south coast 
of England; for the report of its having been gathered in the 
Feeroe Islands, as well as the station “near Dublin,” given by 
Dr. Scott, are, I fear, founded in error. It is assuredly a 
southern species in its affinities and distribution. We have the 
high authority of Turner, that it occurs in Ceylon and in New 
Zealand ; otherwise I should have suspected some mistake in 
these stations also. 
The genera Rytiphlea, Rhodomela and Polysiphonia have so 
many points of structure in common, and differ by characters of 
such secondary importance, that it is sometimes a question to 
which a plant should be referred. The articulated Polysiphonie 
indeed, are readily enough distinguished from the species of the 
two former genera; but it is by an artificial character. For 
species otherwise closely related, as P. subulifera and P. fruti- 
culosa, would, were the genus divided on this character, be 
placed in opposite groups. ‘This would hardly be considered 
natural. But then it becomes a question how the ¢xarticulate 
Polysiphonee are to be separated from the hodomele and 
ytiphlee. Natural habit generally decides it, for there is 
little structural difference. In the true Rhodomele, mdeed, as 
R. subfusca, and RK. lycopodioides, the absence of a joimted axis, 
composed of a circle of elongated cells, affords a ready character. 
But some of the exotic species have more or less evident traces 
of such a structure. In ytiphlea, as here defined, this struc- 
ture exists ; and there is nothing to distinguish the group from 
the inarticulate Polysiphonie, except the position of the ¢etra- 
spores, and some difference of habit. 
Vig. 1. RytrpHima Prvasrrorpes : —of the natural size. 2. A branch with 
stichidia. 3. A stichidium. 4. A tetraspore. 5. A branch with ceramidia. 
6. A ceramidium. J. Spores, from the same. 8. A longitudinal section of 
the frond. 9. A transverse semi-section of the same:—all more or less 
magnified. 
