MARINE ALGJE. 15 



to the right and left, some fifteen secondary similar filaments each in its sheath of small cells, (x 25.) 

 Fig. ISb. 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 4;V>.) Fig. 14. Longitudinal 

 section of mature stem, showing the primary axial filament with its branches (secondary filaments) and 

 their anastomoses; all these filaments are distantly articulated, (x 4.) Fig. HI. 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 raniulus showing the primary axial filament 

 in the centre, (x 110.) 



Desmarestia viridis Lain. var. distans, Hook, and Harv. Fig. 1(5. Transverse section of stem, showing 

 a denser medullary tissue in which the primary axial filament lias become obliterated, (x 25.) 



Graciliti-iii. dumontiouks nob. Fig. 17. Antarctic specimen consisting of numerous cuneato-linear 

 proliferations arising from a fragment of an old frond ; natural size. 



PLATE IV. 



G-rttciliiria dumontioidi'S (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. 111. Monostrornatic 

 cortex in surface view, (x 650.) Fig. 20. Arctic plant named by Harvey Halosaccion dumontioides, 

 collected by Dr. Lyall in lat. 7(T N., and preserved in the British Museum ; its proliferations are very 

 long and simply linear ; natural size. 



Phyllopliora aiitarrtica nob. Fig. 21. Plant bearing marginal cystocarps ; natural size. Fig. 21&. 

 Sterile plant bearing large and small proliferations ; natural size. Fig. 22. Longitudinal section of 

 cystocarpic branch, containing a compound cystocarpic nucleus, (x 80.) 



Spongoclonium orthodailum 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. 25, 256. Young procarpia with trichogyne. 



