( 156 ) 



are rather longer than broad ; articulations obsolete in the main stems, 

 which are cellular, firm, and rigid, scarcely adhering to paper. Colour, a 

 brownish olive. 



This fine species, perhaps the finest of the genus — one, by the way, 

 which is not very remarkable for the beauty of its forms — is said to 

 become more common in the northern than on the southern shores; but 

 our specimens are all from the south of England, although its occurrence 

 on the shores of Scotland is said to be not rare. 



It may be readily known from its congeners by its closely pectinated 

 stems, and long, slender, generally simple but rigid pinnae, standing out 

 like minute wires from the branches. The finest specimens are generally 

 found beneath low-water mark, which seems to be its favourite habitat, 

 although it is occasionally met with in rock-pools between tides. 



The fructification of the Splmcelarioe is but imperfectly understood, 

 and that of the present species, among several others, appears to be 

 unknown. 



The apices of the branches are said to be often fasciculate, but in our 

 specimens they are very imperfectly so. 



EXPLANATION OF PLATE CLXXIIL 



Fig. 1 . — Sphacelaria plumosa, natural size. 

 2. — Portion of a plumule. 

 8. — Portion of a pinnule. 

 4. — Section of an old stem. 

 5. — Semisection of an old stem. All raasnified. 



