If the world. were aosoluetly static, 
counter to this hypothesis. 
Age and Area would supply an obvious working principle; but the 
greatest land-masses of the world have not been static and the result¬ 
ing dispersals of floras is most complex. In view of the great in¬ 
fluence of the historic and an endless series of edaphic and other 
factors, our studies should be directed toward a clear elucidation 
of these positive forces and above all to a thorough knowledge Ox the 
plants themselves. Until we know our plants and the complex factors 
to which each of them and the various associations of them are respond¬ 
ing we can make little progress in the satisfactory working out of 
unive r sa1 laws. 
