RHODOSPERMEA. 205 
tufted filaments. The name is in honour of two French algologists, the 
brothers Crouan, of Brest. 
Halurus equisetifolius, better known by its former name, Grifithsia 
equisetifolia, is, in appearance (though not in colour), almost a counterpart 
of Cladostephus spongiosus. This curious plant was originally included in 
the genus Griffithsia. Its new name signifies “ equisetum-like sea-tail,”’ in 
reference to the whorled tufts of branched incurved ramuli, which are set 
with perfect regularity round the nodes of the stems and branches, in a 
very similar manner to those of the Hquisetw, or ‘*horse-tails’’’ of our 
lanes and meadows. The fronds of this plant are from 4in. to Ift. in 
length; but only young plants, from 3in. to din. long, make good book 
specimens, owing to the robust growth and thickly tufted branches of 
this species, which turn a very dark or dirty brown in drying ; otherwise, 
in early growth, the whorled ramuli of the young branches are a brilliant 
rose-red. Fig. 190, a, represents a terminal branch, somewhat enlarged, 
Fig. 190. (a) Halurus equisetifolius ; (b) Grifithsia barbata. 
showing the order of growth of the whorled ramuli, and the sta!ked 
involucres containing favelle, which arise from amidst the tufts. This 
species is taken very frequently on the south British shores. It is 
perennial, and is in perfection in summer. There is a beautiful variety of 
this plant, which formerly ranked as a distinct species, under the 
name Halurus equisetifolius, var. simplicifilum. One or two British 
localities have been recorded as habitats for this rarity, but I have never 
met with it on any of the British shores. The genus Grifithsia, named in 
honour of Mrs. Griffiths, of Torquay, is a large group of crimson, filiform, 
articulated alge, the fronds of which consist chiefly of string-like branches 
of elongated transparent cells or joints, within each of which is contained 
a long bag-like ceil of brilliant red endochrome: The type of this beauti- 
ful genus is the plant known as Griffithsia corallina (Fig. 191), the fronds of 
