Favellæ bi-)obed, large, formed from truncated plumules. Cohur a
brownish-red, becoming orange in fresh water, and darker in drying. Substance
between cartilaginous and membranaceous, adhering, but not very
closely, to paper in drying.
Callithamnion tetragonum, when fully grown, is one of the
largest and most robust and shrubby of the British species of
this charming genus, and, seen under water, is an object of
mncli beauty. In drying, though it sufficiently retains its form,
it loses considerably in elegance, from the pressing together of
the delicate quadrifarious ramuli, which in a state of nature stand
out from the brancldets, giving to the different parts of the
frond a roundness, without confusion, or matting together of the
minutest part. These, in dried specimens, become confounded
together. Its most frequent habitat is on the stems and margins
of the laciniæ of Laminaria digitata, which it frequently fringes
iu the most beautiful manner ; but it is by no means confined
to tliis species, being often seen on some of the smaller Algæ,
as on Codium tomentoswm, Chondrus crispus and others. It
rapidly changes colour in fresh water, assuming a brilliant orange
tint, and giving out a rose-coloured powder. Tbougli a species
of large size, its tetraspores are exceedingly small, mucb smaller
in proportion than those of most other species, and, being borne
near the tips of the smaller and more crowded ramidi may easily
escape detection. The favelloe, on the contrary, are of large size,
and easily seen.
C. tetragonum appears to be of common occurrence on the
shores of Europe, and very probably extends to the opposite side
of the Atlantic. It is very closely, perhaps too closely, allied to
C. brachiatum, Bonnem., which I have, therefore, figured on the
following plate, that the distinctions may be more readily seen.
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Fig. 1. C a l l i t h a m n i o n t b t e a g o n h m :— the natural size. 3. Penultimate
branch, set with plumules. 3. A plumule, hearing tetraspores. 4. Hamulus
from the same. B. A plumule bearing faveUae. 6. Joints of one of
the main branches, to show the veining:— all tiim-e or less magnijied.
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