214, BRITISH MARINE ALGAE. 
orange or yellowish in decay. This species is a summer annual, and is 
found most frequently growing on the stems of the larger algz near low- 
water mark. Very nearly related to the plant just described is the beautiful 
Fig. 196. Callithamnion tetragonum. 
species C. brachiatum (Fig. 197) ; indeed, by some writers it is considered 
merely a variety of C. tetragonum. It is, however, a much more delicate 
plant, especially in the form and finish, so to say, of the branched or tufted 
ramuli, which in this species are gradually tapered from the base, and 
Fie. 197. (a) Callithamnion brachiatum. (b) Callithamnion Brodie. 
(¢) Calluthamnion Hookeri (highly magnified). 
terminate in a sharp point, while in C. tetragonuwm they are narrow 
at the base, bulged out in the central joints, and suddenly pointed at 
the tips. Fig. 197, a, is a highly-magnified ramulus of C. brachiatum, 
