104 THE POSITION OF THE [pt. ii 



where he was heading for. Here was a daring attempt to get a 

 grip at things from the inductive side, and the question was — 

 Which among the general theories will prove to be its goal? 



But the prospects of the new theory at the outset were not 

 promising. Botanists had been incHned to regard the statistical 

 treatment of distribution as illusory, and the believers in what 

 Watson termed "Species-arithmetic" and Humboldt named 

 " Arithmeticae botanices " were few. Yet Hooker, with the seer's 

 outlook, took the true meaning of things three-quarters of a 

 century ago when he wrote: 



All seem to dread the making Botanical Geography too exact 

 a science; they find it far easier to speculate than to employ the 

 inductive process. The first step to tracing the progress of the 

 creation of vegetation is to know the proportion in which the 

 groups appear in different localities, a relation which must be 

 expressed in numbers to be at all tangible (57, Vol. i. p. 438). 



A generation later, when Hemsley at his suggestion took up the 

 preliminary statistical treatment of floras in the introduction to 

 his great work on the botany of Central America (51), Hooker 

 characterised the subject as "that most instructive branch of 

 phj^togeography."' The lode was rich in promise, but he passed 

 it by. How was this? 



It is clear from his lecture on Insular Floras (142), and from 

 different letters written in the sixties, that the Natural Selection 

 theory offered to him "the most hopeful future" for an advance 

 on the problems of plant-distribution from the inductive side. 

 In that lecture he also shadowed out a general notion of " Cen- 

 trifugal Variation operating through countless ages." It appears 

 almost as a suggestion, but the idea had been evidently floating 

 half-formed in his mind ever since he wrote his essay on the 

 Tasmanian flora in the late fifties. It was the nucleus of a theory 

 of Divergence or Differentiation that acquired more definite out- 

 lines as time went on, since it reappears in the intensely interest- 

 ing account of a talk with Darwin which is given in a letter to 

 Huxley in 1888 (57, ii. p. 306). 



We can perhaps imderstand the long intervals of time now. 

 For the confirmation that such a theory would have derived 

 from a line of research instituted on Darwin's lines was denied 

 to him. The two proved to be incompatible. For no inductive 

 process based on Darwin's lines could have found its goal in a 

 theory of centrifugal variation. "1 well remember," Hooker 

 describes in his letter to Huxley in 1888, "the worry which that 



