308 THE SURVIVAL OF THE UNLIKE. [XVII. 



which have been brought in from other climates 

 must, therefore, be chosen as the registers of the 

 meteorological peculiarities of a given region. We 

 need charts giving the zones or life areas of the cul- 

 tivation of the different fruits, and these zonal limits 

 should be constructed from the actual behavior of 

 trees in winter, or in summer, rather than from any 

 assumed theoretical temperature at which trees perish. 

 If constructed from the orchard observations, these 

 limits would become much more than mere isotherms, 

 for trees may be injured quite as much by the alter- 

 nations of temperature, the relative humidity of soil 

 and atmosphere over great areas, the direction and 

 force of prevailing winds, and other features, as by 

 temperature itself. 



There are numerous problems of still more local 

 application which are yet of vital importance to the 

 cultivator, and in the solution of which he has the 

 right to expect the aid of the climatologist. The 

 habitual force and frequency of winds during the sea- 

 sons of maturation of fruits, the prognostication and 

 methods of averting frosts, the influence of wind- 

 breaks and orchards upon local climate, the modifi- 

 cation of climate in consequence of the removal of 

 forests and the clearing of land, the frequency of 

 droughts, the humidity of atmosphere as affecting the 

 spread of fungous diseases and the abilitj' to prog- 

 nosticate serious incursions of these diseases from a 

 study of their general relations to climate, the liabil- 

 ity to hail storms, the nature of the seasonal varia- 

 tions, — these, in addition to the subjects which I have 

 already indicated, are some of the living problems 

 which await us. 



