long, giving the frond an ovate outline, and bearing a second or third series 
of lesser branches. In others, the main stem is once or twice forked, and 
clothed throughout with short lateral branches of nearly the uniform length 
of an inch; and in others (as represented in our figure), the stem is irre- 
gularly forked, the lateral branches more erect, simple or divided, more or 
less fastigiate, and the general outline of the tufts roundish. In all varieties 
the younger portions of the fronds are beset with more or less dense, hair- 
like, jointed ramuli about two lines in length, and issuing without order 
from all sides of the branch. Occasionally these are very few and the plant 
becomes S. nudiuscula, of Kutzing. Tube occupying two thirds of the 
breadth of the stem, divided into joints by transverse diaphragms, placed at 
short intervals; its walls cellular, and the external surface reticulated. 
Tetraspores elliptical, clustered round the bases of the ramuli. Fuvelle 
bi-lobed, or rarely tri-lobed. Colour a dull red, very frequently faded, and 
yellowish white. Substance, of the stem cartilaginous, of the ramuli mem- 
branaceous. 
This plant, which is very local on the British coasts, although 
found in considerable plenty in a few places, is interesting in a 
geographical view, being a native of warm latitudes which reaches 
to its northern limit in this country. Until very recently that Mr. 
Ralfs discovered it on the Welsh coast, it had only been found 
in Britain on the extreme southern shores. It is more plentiful 
in the Channel Islands, and along the French coast, and abounds 
in the Mediterranean ; but the finest specimens are found in the 
Tropical ocean. In Britain it is very generally much discoloured, 
being of a dirty grey or brownish cast, a deformity caused by its 
growing in comparatively shallow water, and in places exposed to 
strong sunshine. 
A plant so widely dispersed is, as might reasonably he sup- 
posed, subject to some variations of character, on which Kiitzing 
has proposed to found several distinct species. In the detailed 
description I have noticed some of these variations, which do not 
appear to me to be of specific value ; and in a very extensive series 
of specimens from different localities I find mnumerable inter- 
mediate forms. The most distinct looking variety, (and it may, 
perhaps, be admitted as a species) is found in Tasmania, and has the 
ramuli pretty constantly whorled, and much denser than usual. 
Fig. 1. SpyR1DIA FILAMENTOSA :—watural size. 2. A transverse section of the 
stem. 3. Longitudinal semi-section of the same, 4. Branchlet with its 
ramuli, bearing tetraspores. 5. Ramulus with detraspores. 6. Branchlet 
bearing favelle. 7. A favella, 8. Spores from the same :—all more or less 
magnified, 
