\m
Ceramium acanthonotum was first distinguished by the late
Capt. Carmichael, of Appin, in whose unpublished ‘ Algm Appin-
enses ’ an excellent description and accurate figure are given.
I t is my fault that in the ‘ British Flora ’, and subsequent works,
it appears only in the rank of a variety. Later observations, on
several of our shores, and comparison of numerous specimens,
from various quarters, have long since convinced me that it is a
true species. Its colour is much darker than that of C. ciliatum,
often an intense purple; and the tufts are usually shorter, and
more densely compacted. These characters, however, are not
sutficiently definite, and an appeal to the microscope may be
necessary. This at once displays the admirable character by which
the species may be recognized, namely, the solitary, three-jointed
spine, arming the outer margin of every joint. The only other
known British Ceramium which has a spine at all similar, is
C.flalelligemm, but that is at once distinguished by its joints
being coloured, not hyaline; not to speak of its very different
branching, and the smallness of its spine.
Kiitzing, in his revision of the genus Ceramium, divides the
species into six distinct genera, one of which he founds on
the present individual, which he distinguishes generically from
other ciliated Ceramia because its tetraspores are erumpent. As
some of my readers may desire to know the characters attributed
to this author s genera, they are here given.
H okmocekas. Frond Jointed; cortical cells collected at the dissepiments in transverse
zones; tetraspores immersed. {Q. diaphanum and its allies ;
thirteen species enumerated.)
G ongeocebas. Frond Jointed; cortical cells collected at the dissepiments in
transverse zones; tetraspores erumpent. (C. Deslongchampsii, and
five others)
E ohin o ce ea s . Frond jointed, zoned and aculeated at the joints; tetraspores
immersed. (C. ciliatum, and nine others.)
Acanthocbbas. Frond jointed, zoned and aculeated at the joints; tetraspores
erumpent. (0. acanthonotum)
C ee am ium . Frond filiform, consisting of a jointed central axis, and a cortical,
continuous layer of cells, destitute of cilia or sp in es ; tetraspores
immersed in the cortical layer. ( 0 . ruhrum., fic.)
Centbocebas. Frond as in Ceramium, hut furnished at the joints with prickles
or spikes; tetraspores erumpent. (C. clamlatum, andfme others)
i i l
Fig. 1. Ceeamium acanthonotum :—tu ft o f the natural size. 2. Portion of a
filament. 3. Small part of the same, with tetraspores. 3. SmaU portion
of a filament, with ffavella, in situ ;— all more or less magnified.