XYI 



GEOGRAPHICAL DISTRIBUTION OF PLANTS 

 By Sir William Thiselton-Dyer, K.C.M.G., CLE., Sc.D., RRS. 



The publication of The Origin of Species placed the study of 

 Botanical Geography on an entirely new basis. It is only necessary 

 to study the monumental G^ographie Botanique raisonn^e of 

 Alphonse De Candolle, published four years earlier (1855), to realise 

 how profound and far-reaching was the change. After a masterly 

 and exhaustive discussion of all available data De Candolle in his 

 final conclusions could only arrive at a deadlock. It is sufficient to 

 quote a few sentences : — 



"L'opinion de Lamarck est aujourd'hui abandonn^e par tons les 

 naturalistes qui ont etudi^ sagement les modifications possibles des 

 etres organises. . . . 



" Et si Ton s'^carte des exag^rations de Lamarck, si Ton suppose 

 un premier type de chaque genre, de chaque famille tout au moins, 

 on se trouve encore h regard de I'origine de ces types en pr(5sence de 

 la grande question de la creation. 



" Le seul parti h prendre est done d'envisager les etres organises 

 comme existant depuis certaines dpoques, avec leurs qualit(5s par- 

 ticuli^res^" 



Reviewing the position fourteen years afterwards, Bentham re- 

 marked: — "These views, generally received by the great majority 

 of naturalists at the time De Candolle wrote, and still maintained 

 by a few, must, if adhered to, check all further enquiry into any 

 connection of facts with causes," and he added, "there is little doubt 

 but that if De Candolle were to revise his work, he would follow the 

 example of so many other eminent naturalists, and. . .insist that the 

 present geographical distribution of plants was in most instatices a 

 derivative one, altered from a very different former distribution^." 



Writing to Asa Gray in 1856, Darwin gave a brief preliminary 

 account of his ideas as to the origin of species, and said that 



1 Vol. II. p. 1107. 2 Pres. Addr. (18G9) Proc. Linn. Soc. 1868—69, p. Ixviii. 



