MARINE ALGAl. UD 
to the right and left, some fifteen secondary similar filaments each in 1ts sheath of small cells. (x 25.) 
Fig. 13). Part of the same, showing an ensheathed secondary filament apparently containing tyloses ; the 
large cavity on the left is merely an ordinary cell of the thallus. (x 450.) Fig. 14a. Longitudinal 
section of mature stem, showing the primary axiai filament with its branches (secondary filaments) and 
their anastomoses; all these filaments are distantly articulated. (x 4.) Fig. 144. Small portion of 
longitudinal section of stem, showing a secondary filament faintly indicated within its sheath of small 
cells. (x 340.) Fig. 15. Transverse section of an ultimate ramulus showing the primary axial filament 
in the centre. (x 110.) 
Desmarestia viridis Lam. var. distans, Hook. and Hary. Fig. 16. Transverse section of stem, showing 
a denser medullary tissue in which the primary axial filament has become obliterated. (x 25.) 
Gracilaria dumontioides nob. Fig. 17. Antarctic specimen consisting of numerous cuneato-linear 
proliferations arising from a fragment of an old frond ; natural size. 
PLATE IV. 
Gracilaria dumontioides—(continued). Fig. 18. Transverse section of the above-mentioned fragment 
of old frond near its margin, where the cortex becomes thicker and polystromatic ; the internal tissue 
consists of large cells permanently flattened in drying the plant. (x 400.) Fig. 19. Monostromatic 
cortex in surface view. (x 650.) Fig. 20. Arctic plant named by Harvey Halosaccion dumontioides, 
collected by Dr. Lyall in lat. 76° N., and preserved in the British Museum ; its proliferations are very 
long and simply linear ; natural size. 
Phyllophora antarctica nob. Fig. 21a. Plant bearing marginal cystocarps; natural size. Fig. 210. 
Sterile plant bearing large and small proliferations; natural size. Fig. 22. Longitudinal section of 
cystocarpic branch, containing a compound cystocarpic nucleus. (x 80.) 
Spongoclonium orthocladum sp. nov. Fig. 23. Part of plant; natural size. Fig. 24. Rather 
diagrammatic representation of apical part of a branch, showing the long, straight, subulate ramelli. 
(x 35.) Figs. 25a, 25b. Young procarpia with trichogyne. 
