RHODOSPERME. 227 
scopic parasites, which, particularly on account of their rarity, are 
the delight of all enthusiastic algologists. Among these minute parasitic 
plants, may occasionally be found, in tiny scattered tufts, less than a 
. quarter of an inch high, the rare and curious species, VU. sparswm, the 
filaments of which are nearly straight, with blunt tips, and very sparingly 
branched, rarely more than a single branch or ramulus being thrown 
out from one side of the erect filaments near the terminal portions. 
The colour of this plant is a pinky-red. Its most frequent place of 
growth is on the stem or decaying frond of Laminaria saccharina (Fig. 
43.) CO. Daviesii is most generaliy parasitic on the decaying fronds of 
Ceramium rubrum (Fig. 176) in rock pools about half-tide level. I once 
dredged in Plymouth Sound a very fine plant of Sporochnus pedunculatus 
(Fig. 55), every branch of which was infested throughout with most 
luxuriant specimens of this lovely little Callithamnion, beautifully in 
fruit.. The little tufts of this plant are about a quarter of an inch 
4 
| 
} 
\ 
J 
4d 
Q 
Fig. 205. Magnified filaments—(a) Callithamnion Rothii; (b) C. floridulum ; 
(ec) C. mesocarpum; (d) C. Daviesii; (e) C. virgatulum. 
high, the branches are alternate, and at intervals of four or five 
joints apart, a short branch is thrown out, which bears on its inner 
face a series of small erect ramuli, the longest of which is nearest the axil, 
so that the three are nearly on a level at the tips. Tetraspores, when 
present, are attached to these axillary ramuli. Part of a terminal branch 
is represented at d, Fig. 205. C. virgatulum, or the twig-like callitham- 
nion, is considered by some writers to be merely a variety of the 
preceding species. It is also parasitic on Ceramium rubrum. The little 
lateral branches are produced much in the same way as those of the 
foregoing, but the ramuli are so short that they appear to consist merely 
of a single cell arising from one side only of the stems and branches. 
A branch of this plant is represented at e, Fig. 205. The tufts of this 
little parasite are about a quarter of an inch long, of a pinky-red colour, 
and they sometimes so completely envelope the fronds of the plant of 
