L.M.B.C. MEMOIRS. 



No. IV. CODIUM. 



BY 



E. J. Haevey Gibson, M.A., P.L.S., and Helen P. Auld, B.Sc. 



Intboduction. 



Among the heterogeneous collection of Algge, marine and 

 fresh-water, known to Botanists as Chlorophyceae, none, 

 perhaps, are more interestmg from the morphological 

 point of view than the Siphoneae. The interest attach- 

 ing to them centres in the fact that the vegetative thallus, 

 though not infrequently of immense size and complicated 

 structure, is, in reality, produced by the extension, 

 branching and modification of a single "cell" or coeno- 

 cyte, possessed of an indefinite number of nuclei. In 

 such forms as Valonia, the primitive spherical cell form 

 is retained ; in VaucJieria, the thallus becomes filamentous 

 and sparingly branched; in Gaulerpa, Bryopsis, &c., the 

 branching is more extensive and symmetrical. In other 

 types, again, the thallus consists of an aggregation of 

 hyphse, held together by a deposition of calcium carbonate, 

 e.g., Halimeda, &c., by holdfasts of diverse form, e.g., 

 Udotea, Struvea, &c., or by intimate interweaving of the 

 filaments themselves, a mode of union illustrated by the 

 subject of the present Memoir, viz., Codium. 



