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well adapted to wind-transport : ' If we assume that a 

 tree flowers and fruits at 30 years of age and the fruits 

 are disseminated to a distance of 100 yards, that the 

 furthest fruits always germinate and so continue in 

 one direction, it will be seen that under such most 

 favourable circumstances the species can only spread 

 800 yards in 100 years, and would take 58,0(50 years 

 to migrate 100 miles '(20). 



There is, however, one type of distribution — 

 wliat is called discontinuous distribution — to which 

 special attention should be directed on account of its 

 intimate association with questions relating to the 

 past history of living organisms. Many examples 

 might be quoted from both the animal and plant 

 kingdoms in support of the view that discontinuous 

 distribution is a criterion of antiquity. When identical 

 or very nearly identical plants occur in regions 

 separated from one another by areas in which the 

 particular species is unknown, the inference is either 

 that the surviving individuals are remnants of a large 

 number formerly distributed over a wider continuous 

 area, or that in the course of evolution similar con- 

 ditions in widely separated areas led to the production 

 of identical types. The former view is much the more 

 probable : it is consistent with the conclusions arrived 

 at on other grounds as to the connexion betAveen 

 discontinuous distribution and ancient lineage. The 

 explanations of the widespread occurrence among 



