RHODOSPERME. 21] 
of species in this very delicate group of seaweeds, is entirely out of the 
question. Dr. Harvey in his original description of the British Calli- 
thamnie, classed them under six different characteristic sections, an 
arrangement which has always appeared to me so admirable, that not- 
withstanding the difficulty of arranging my illustrations in groups con- 
venient for my purpose, I intend to follow the order of Dr. Harvey’s 
arrangement in my descriptions of the species, «s closely as possible. 
Section 1. Cruciata, contains all those species in which the ramuli are 
placed on the branches in pairs, generally exactly opposite to each other. 
Callithamnion plumula is one of the most brilliant of this group. It is 
one of the commonest and most widely dispersed of the tribe, being 
Fic. 195. (a) Favellx of Callithamnion plumula; (b) Callithamnion jloccosum ; 
(ce) Callithamnion Turneri, magnified. 
found from the Orkneys to the South of Devon. The beauty and regularity 
of its growth, combined with its graceful outline, its branched froads 
(which are like exquisitely arranged plumes of rose-tinted feathers), have 
long stamped this plant as a universal favourite. The order of growth 
in every part is very remarkable. Hach branch and branchlet has its 
exact counterpart, and all the articulations throughout the plant bear 
each a similar pair of pectinated or comb-like branchlets. Tetraspores, 
like tiny glistening rubies, are seated on the upper side of the terminal 
ramuli. Favelle, which are produced in clusters, are attached to the 
joints of the main branches, as represented at a (Fig. 195.) There is a 
