RHODOSPERME. 213 
alternate along the stems, are bare for about half their length, and then 
produce the little, erect, opposite, spine-like ramuli, which are referred to 
in the specific name of the plant. Tetraspores are seated on the sides of 
the winglets or terminal branchlets. The brownish-red colour of its 
’ fronds sometimes betrays it in its muddy habitat, but it requires ex- 
perience and sharp eyes to detect it at any time. 
C. pluma, a minute species, rarely above half an inch high, grows in little 
erect velvety tufts on the stems of Laminaria digitata (Fig. 46); but is 
very rarely met with, though it occurs in widely separated situations. 
It partakes somewhat of the character of the preceding species, in having 
the upper part of its fronds set on each side, but sometimes on one side 
only, with short setaceous ramuli. This little plant is rather like small forms 
of C. Turneri (Fig. 195). The colour is a bright red; but the whole plant is 
so minute, that, except as a curiosity, itis hardly worth the trouble of 
mounting. Section 2, Fruticosa, includes the species which are essentially 
shrub-like, the main stems being more or less opaque, the basal joints more 
particularly, being coated within or traversed by numbers of filaments, 
which in some species render the jointing nearly undistinguishable. 
The ramuli in all the plants of this group are placed alternately on the 
branches. C. arbuscula is a particularly robust and shrub-like species. 
The branches are so densely clothed with a second series of shorter 
branches, all of which are set with numerous closely placed minute 
pinnated, or winged ramuli, that, unless the whole be considerably 
pruned or thinned out, it is quite impossible to make anything of a 
specimen of this bushy plant. The fronds are from three inches to about 
six inches long, and, in the growing state, are of a very dark blood-red 
colour. This species is, I believe, perennial. It is not found on any of 
the southern shores, but is generally met with on the north-western coasts 
of Scotland and Ireland. I never failed finding it in the deep rock pools 
of Whiting Bay, in the Isle of Arran; but all the specimens I took there 
were thrown up from deep water. Even at the lowest spring tides I never 
found it growing. The tetraspores are produced on the inner side of 
the ramuli; favelle are usually bi-lobed. Next to this northern species 
of Callithamnion, the common C. tetragonwm is perhaps the most bushy 
and shrub-like of this section. Well-grown plants, such as we have 
attempted to depict at Fig. 196, are more or less tufted, each frond having © 
a main stem set with lateral branches, which gradually diminish in length 
as they approach the summit, giving an elegant pyramidal outline to the 
frond. All the branches are set with a second and third series, and the 
tufts of ramuli, which are produced abundantly on each side of the 
branches, are somewhat incurved; the joints are narrow at the base, 
then gradually widen and become suddenly pointed at the tips. The 
tetraspores, which are very minute, are produced near the tips of 
these terminal ramuli. Favelle of large size, solitary, or bi-lobed ; when 
the latter, the large oval masses are attached to the upper forked ramulus 
of the terminal branchlets. The colour is a dark brown red, turning an 
