Distribution of the Lamiiiariacece. 359 



The districts enumerated above are the principal geographical 

 districts in which kelps are found. There are however several 

 more or less isolated kelp-localities which are of great importance 

 when the causes of distribution are being discussed. Such localities 

 are the Society Islands, Kerguelen Land, St. Paul Islands, the 

 Crozets, and the Canary Islands, the latter of whose species have 

 already been enumerated in the table among the species of western 

 Africa. 



At Kerguelen Land, nearly midway between Australia and the 

 Cape of Good Hope but decidedly to the South are found growing: 



Macrocystis pyrifera, Ag. 



Lessonia fuscescens, Bory, 

 and at Heard Island, 250 miles south of Kerguelen Land are found 



.Lessonia nigrescens, Bory. 



" ovata, Hook. & Harv.^ 

 At St. Paul and the Crozets, also approximately half-way between 

 the Cape of Good Hope and western Australia but more to the 

 north or west, are found : 



JEcMonia huccinalis (L.), Hornem. 



Laminaria pallida, Grev. 



Macrocystis pyrifera, Ag., 

 and at Tahiti and the other Society Islands, midway in the Pacific 

 Ocean and in the Torrid zone (10-20° S. long.) are found: 



Macrocystis pyrifera, Ag. 



Lessonia Suhriiy J. Ag. 

 " nigrescens^ Bory. 



The Laminariaceae, as mentioned above, are inhabitants of the 

 colder waters of the globe. At the north, they extend up so far as 

 there is suitable bottom which is free from permanent or very 

 nearly permanent ice ; and in the south, they extend down so far 

 as the ice will permit.'* They do not occur in the tropical waters 

 nor in those of the warmer temperate regions except as the tempera- 

 ture of these waters may be brought down to th^ proper degree 

 of coldness by the current from the polar regions. 



It is the temperature that limits the distribution of the kelps and 

 that too, the summer temperature, as heat not cold is inimical to their 

 growth. They can endure almost any degree of cold that occurs, 

 even in polar waters but leadily die and decay where the waters 



^ Cf. Dickie, Jour. Proc. Linn. Soc, vol. xv, p. 47, 18T6. 

 - Hooker, Flora Antarctica, Pt. 2, p. 465. 



