LEOPOLD BUCH. IO7 



I must first mention tlie great German geologist, Leopold 

 Buch. Important observations as to the geographical dis- 

 tribution of plants led him to the following remarkable 

 assertion in his excellent "Physical Description of the 

 Canary Islands " : — 



"The individuals of genera, on continents, spread and 

 widely diffuse themselves, and by the difference of localities, 

 nourishment, and soil, form varieties ; and being in conse- 

 quence of their isolation never crossed by other varieties, 

 and so brought back to the main type, they in the end 

 become a permanent and a distinct species. Then, perhaps, 

 in other ways, they once more become associated with other 

 descendants of the original form — which have likewise 

 become new varieties — and both now appear as very distinct 

 species, no longer mingling with one another. Not so on 

 islands. Being commonly confined in narrow valleys or 

 within the limit of small zones, individuals can reach one 

 another and destroy every commencing production of a per- 

 manent variety. Much in the same way the peculiarities or 

 faults in language, originating with the head of some family, 

 become, through the extension of the family, indigenous 

 throughout a whole district. If the district is separated and 

 isolated, and if the language is not brought back to its 

 former purity by constant connection with that spoken in 

 neighbouring districts, a dialect will be the result. If natural 

 obstacles, forests, constitution, form of government, unite 

 the inhabitants of the separate district still more closely, 

 and separate them still more completely from their neigh- 

 bours, the dialect is fixed, and becomes a completely 

 distinct language." (Uebersicht der Flora auf den Canarien, 



a 133.) 



