202 BRITISH MARINE ALG. 
branchlets, highly magnified, one of which bears bi-lobed favellz at the 
tip, partly embraced by a few curved ramuli, the other produces tetra- 
spores on the tips of the lateral cellules which project on each side 
from the large central cells of the pinnules. This species (like the former) 
is perennial, and is in perfection in summer. It grows on the sides of 
shady rocks near low-water mark. The colour is a dark brown-red, 
and the plant, being somewhat flaccid, adheres closely to paper in drying. 
The genus Dudresnaia, dedicated to M. Dudresnay, a French naturalist, 
contains only one British species, Dudresnaia coccinea, represented at a, 
Fig. 188, by a couple of lateral branches. This curious but very beautiful 
plant is equally difficult to display effectively and to figure satisfactorily. 
Its delicate rose-red fronds are so tender and gelatinous, that they require 
several hours to drain off the paper on which they are Jaid out, before 
the calico and blotters can be placed on them, and the pressure applied ; 
but with careful management they make the most exquisite specimens, 
for they retain their lovely rosy tints and adhere so firmly to the paper 
that it is impossible to remove them. This species is rare, being an 
inhabitant of deep water. I have taken it on the beach at Brighton, also 
in Torbay, and have dredged most beautiful specimens in Plymouth Sound. 
A microscopical examination of this plant reveals a beautiful structure. 
All the branches appear to be composed of articulated, slightly coloured, 
longitudinal filaments, which have disposed around them whorled tufts of 
rose-coloured branched fibres, extremely flaccid and of the utmost tenuity. 
In the water these dichotomons, or forked fibres, radiate around the 
stems ; and when the plant is in fruit the branches appear as if studded 
with rubies, favellidia being borne at intervals among the shorled fila- 
ments; or tetraspores, when present, terminating a ramulus of the 
dichotomous fibres. A terminal branch, magnified, is represented at }, 
Fig. 188, showing the fruit among the whorled filaments ; and ¢ is a more 
highly magnified forked fibre, bearing a four-parted tetraspore, which is a 
transformation of its terminal cell. This charming plant is a summer 
annual, and is, I believe, peculiarly a southern species. 
Crouania atlenuata is an extremely rare, but remarkably beautiful 
plant, parasitical on Cladostephus spongiosus, and sometimes on Corallina 
officinalis. This also is a southern species. It is found on the Cornish 
coast near Penzance, and at the Land’s End. I have taken it several 
times at Plymouth, but nowhere else. Its beauties are microscopic. 
Fig. 189 represents a branch of Cladostephus (one of the olive weeds), on 
the tips of which Crowania attenwata leves to dwell. The little tufts of 
this parasite are rarely over 2in. high. They are represented at a, Fig. 189, 
- a quarter of the natural size; b is one of its forked branches highly 
magnified, and c isa portion more highly magnified, to show the dense tufts 
of multifid ramelli or branched filaments which are set around the stems 
and branches with the most perfect regularity. These little tufts are 
whorled round the joints of the stem, which is a syphon containing a broad 
tube, filled with dark red endochrome. Tetraspores are seated on these 
