322 SIR JOSEPH DALTON HOOKER 



more nearly those of China than do those of the Pacific Slope. 

 In resolving these and other problems it was not only the 

 vegetation itself that was studied. The changes of climate in 

 geological time, and of the earth's crust as demonstrated by 

 geologists, formed part of the basis on which he worked. For it 

 is facts such as these which have determined the migration of 

 Floras. And migration, as well as mutability of species, entered 

 into most of his speculations. The Essays of this magnificent 

 series are like pictures painted with a full brush. The boldness 

 and mastery which they show sprang from long discipline and 

 wide experience. 



Finally, the chief results of the Phyto-Geographical work of 

 himself and of others were summed up in the great Address on 

 "Geographical Distribution" at York. The Jubilee of the British 

 Association was held there in 1881. It had been decided that 

 each section should be presided over by a past President of the 

 Association, and he had occupied that position at Norwich in 

 1868. Accordingly at York Hooker was appointed President of 

 the Geographical Section, and he chose as the subject of his 

 Address "The Geographical Distribution of Organic Beings." 

 To him it illustrated " the interdependence of those Sciences 

 which the Geographer should study." It is not enough merely 

 to observe the topography of organisms, but their hypsometrical 

 distribution must also be noted. Further, the changes of area 

 and of altitude in exposed land-surfaces of which geology gives 

 evidence, are essential features in the problem, together with the 

 changes of climate, such as have determined the advance and 

 retrocession of glacial conditions. Having noted these factors, 

 he continued thus : " With the establishment of the doctrine of 

 orderly evolution of species under known laws I close this list of 

 those recognised principles of the science of geographical distri- 

 bution, which must guide all who enter upon its pursuit. As 

 Humboldt was its founder, and Forbes its reformer, so we must 

 regard Darwin as its latest and greatest law-giver." Now, after 

 thirty years, may we not add to these words of his, that Hooker 

 was himself its greatest exponent ? 



And so we have followed, however inadequately, this great 

 man into the various lines of scientific activity which he pursued. 



