SOME ECONOMIC ASPECTS OF SHORE LIFE 297 



the shore fauna in general and on fishes in particular. This 

 is a question which is discussed at length by Sauvageau, 

 who disagrees with Gloess's statement that Laminaria when 

 cut quickly grows anew. According to the former writer, 

 the Laminaria of the French coasts, when the stipe is severed, 

 no matter at what point, never continue to grow whether 

 from the stipe or from the ** roots." Though the repro- 

 ductive zone is situated at the junction of stipe and frond, 

 growth by cell division only begins at a point of the frond 

 well above the base, and though theoretically it might be 

 possible to sever the weed so as to make sure of its growing 

 anew, in practice this is not feasible. The chief points 

 to be considered in connection with this question are the 

 situation of the conceptacles, the length of life of the parti- 

 cular species, and the season of reproduction. Delage (1913) 

 is of the opinion that an increased use of Laminaria for 

 industrial purposes might prove a serious menace to the 

 inshore fisheries, not because of the shelter these afford 

 to the fishes themselves, but on account of the large inverte- 

 brate population which lives among them and on which the 

 fish feed. 



As an example of the many miscellaneous uses which have 

 been made of algae we may mention the way in which their 

 highly hygroscopic qualities were utilised by the Germans 

 in the construction of a delayed-action bomb. These 

 bombs, which were employed in the late war, exploded 

 after lying for a time in a pool of water or in any damp place. 

 The explosion was produced by the swelling of a portion of 

 the stipe of L. cloustoni breaking a glass bulb and so bring- 

 ing sulphuric acid into contact with chlorate of potassium. 

 In other grenades, a needle, pushed by the expanding 

 Laminaria, came into contact with a capsule of fulminate 

 of mercury (Sauvageau, op. cit.). 



Injurious Algse. — A curious instance of the adverse effects 

 of an alga upon a commercial enterprise may be given. The 

 spread of the species Colpomenia sinuosa has been mentioned 

 elsewhere (see Ch. Ill, p. 54), and Mangin (1907) describes 

 its effects upon some oyster-beds on the French shores at 



