144. BRITISH MARINE ALG. 
fronds vary from 3in. to 6in. in length, and are irregularly branched from 
the base, the branches terminating in a fork; some are trifid, and others 
have a terminal tuft of even four or more ramuli of different lengths. 
This plant grows on rocks, but its most frequent place of growth is on the 
shells of the Balani or sea-acorns. Its colour is a dull brownish purple. 
Favellidia, containing a globular mass of spores, are produced within 
the marginal filaments of the frond. This species is annual. It is widely 
dispersed, but nowhere very abundant. Helminthocladia (formerly Nema- 
leon) purpurea, is a rare deep-water plant, though occasionally found 
growing at extreme low-water mark, but of stunted form and sparingly 
branched. Specimens from deep water are from 12in. to over 2ft. in length. 
The main stem is tapered at both ends, and is set on each side with 
branches of similar form, which are irregularly and sparingly provided 
with ramuli. Instances, however, occur, of very luxuriant forms of this 
species, and in such, the stem and branches are very thick, round, and soft 
to the touch, and are plentifully, but always irregularly, set with ramuli of 
various lengths. Two lateral branches from a large deep-water specimen 
are represented at Fig. 133, a third less than the natural size. The colour 
of this plant in the living state is a rich reddish purple, and, under the 
microscope, as Dr. Harvey has so beautifully said, in describing its 
structure, ‘the axis of the stem is composed of colourless, branching, 
Fig. 1383. Helminthocladia purpurea. 
longitudinal threads, and the apical cells of the horizontal filaments, which 
are thrown out on all sides to the circumference, cause the stems and 
branches of this plant to appear as if studded with red beads set in trans- 
parent glass.’ Round masses of spores are concealed within these 
radiating filaments. This fine species is a summer annual. It occurs 
