77 



it may have been directly introduced to our shores by vessels ; or 

 conceivably with the consignments of young oysters that are 

 imported from France to be u fattened" on the British culture- 

 grounds, from whence it may have towelled along the coast. 



The naturalisation of a marine alga on foreign shores is 

 interesting and uncommon. Cases are known in which algae 

 have been introduced and may now be found settling down 

 and slowly spreading in the immediate vicinity. The Japanese 

 Bonnemaukmia hamifem is a case in point. This alga is 

 confined to certain spots on the south coast of England, and 

 is found in very small quantity only. With Colpomenia it is 

 otherwise. For over a century it has been recognised from the 

 Mediterranean region, but, as far as known, has not during that 

 period spread in a northerly direction. By some means it lias 

 now appeared in various localities in France and England, where 

 it thrives and spreads rapidly, the external conditions appearing 

 to be perfectly suitable to vigorous growth. The presence of 

 warm currents due to the Gulf Stream would probably account 

 for a southern alga being able to flourish in the English Channel, 

 though it is not easy to see why Colpomenia should not have 

 spread previously along the coasts of Spain and Portugal, which 

 receive the full benefit of the Gulf Stream. M. Bornet, in a 

 letter to Mr. Holmes, suggests that Colpomenia has been brought 

 to Vannes by the vessels that convey living lobsters from Portugal 

 to be cultivated in the Gulf of Morbihan. This explanation is 

 possible enough, although as noted above there is no certain 

 record that the plant occurs on the Portuguese coast. 



XIV. and XV. 



Literature. 



M. 0. On the structure of Hyd 

 oerical Memoirs. Part ii. 1903. n 



es 



2. Fabre-Domergue. Une invasion d'Algues meridionales 

 {Colpomenia sinuosa) sur les huitres de la riviere de Vannes. 

 Comptes Rendus, CXLII. 1907, pp. 1223-1225. 



3. Sauvageau, C. A propos du Colpomenia sinuosa signale 

 dans les huitrieres de la riviere de Vannes. Bulletin scientifique 

 d'Arcachon, IX. 1906, pp. 35-48. 



4. Corbiere, L. Sur Tapparition a Cherbourg du Coipoment 

 sinuosa. Bull, de la Soc. Bot. de France, L1V. 1907, pp. 280-283. 



5. MANGIN, L. A propos du Colpomenia sinuo /, (Roth) Derb. 

 et Sol. Bull, de la Soc. Bot. de France, LIV. WW, pp. 283-284. 



G. Mangin, L. Sur Fexistence du Colpomenia sinuosa dam la 

 Manche. Comptes Rendus Soc. Biol. Paris, L; [I. 1907, pp. 71*3- 



79r>. 



7. Fauvel, P. Sur la presence du Colpomenia sinuosa a 

 Cherbourg. La feuille des Jeunes Natnralistes, 1907, p. 146. 



