75 



walls, and by the structure, which is cellular and not filamentous, 

 Leathesia also is usually irregularly lobed even when quite 

 young, and has a resiliency which is lacking in Colpomenia* 



The history of the appearance of Golpomenia sinuosa on the 

 West Coast of France and in the Ei w 

 In 1906, M. Fabre-Domergue, Inspector-General of Marine Fisheries, 

 recorded (2) the appearance of a seaweed at Vannes, in the Gulf 

 of Morbihan, which caused the oyster-cultivators considerable 

 anxiety. The plant was determined by Bornet to be Colpomenia. 

 Fabre-Domergue states that the cultivators gave the seaweed the 

 name of "Ballons" from the fact of their becoming, after exposure 

 to the atmosphere at the lowest tides, partially filled with air, and 

 floating to the surface of the water at the return tide. Considerable 

 damage was done to the oyster-beds by the "ballons" not infre- 

 quently bringing with them to the surface the joung oysters 

 amongst which they had been growing. The author quotes a 

 communication from Bornet, stating that the alga was not positively 

 known to occur north of Cadiz, and that records of its presence 

 on the North Coast of Spain-are unreliable, especially as Leathern a, 

 which is found on that coast, is not cited in Lazaro's catalogue. 

 Amongst methods employed by the oyster-cultivators to destroy 

 Colpomenia, the only one which hac 



cessfuh was that of breaking the "ballons" by sweeping the 

 oyster-beds with bundles of prickly branches (" fagots epineux "). 

 Fabre-Domergue suggested that the special conditions of Vannes 

 in the Gulf of Morbihan were favourable to the growth of this 



measur 



. , - that „„ 



probably disappear. 



At the end of the same year Sauvageau (3> published a paper on 

 the occurrence of Colpomenia on the oyster-beds of the river 

 Vannes, and recorded it from Belle Isle and Qniberon, two new 

 localities in the same neighbourhood. From its distribution and 

 abundance, the author believed that it had 1 en introduced 

 several years previously and had already become acclimatised. 

 The floating of the alga is explained by Sauvageau in the following 

 manner. "Le Golpomenia tres jeunes est massif ; il se creuse en 

 augmentant de volume. II a nne base etroite qui est son point 

 d'attache ; soit par disorganisation localisee, soit par suite de 

 Tirregularite du support, cette base presente des ouvertures par 

 lesquelles l'eau s'ecoule. Au retour du flot, l'eau penetre dans 

 l'Algue par dessous, emprisonne l'air et constitue le ballon, qui 

 est capable de soulever un support non fixe. Normalement, le 

 Colpomenia etant adherent- au rocher, ou a des Algues fixees, n'est 

 pas transports par le courant comme celui de la Riviere de 

 Vannes/' Sauvageau also remarks that the method of breaking 

 the " ballons " though efficacious in preventing the tendency to 

 float is neither curative nor preventive, in fact the reverse, since 

 the spnnin.c'ia-bearing fragments of the algae are borne away by 

 the currents and dispersion promoted. The number of oysters 

 carried awav from the beds is considerable, at times so much so, 



net*. 



as 



several botanists 



Cherbourg. Corbiere 



added 



