X. CLniATE OP PLANTS. 473 



England combined with the winters of warmer latitudes. 

 Their unheated or " cold " frames also admit of further 

 varied combinations between the temperatures of the 

 seasons, with choice of sim or shade. Simply by aid of 

 glass, and without fires, all or any of our natural seasons 

 can be made warmer, and may be made either more 

 equable or less equable, for the plants placed within such 

 frames. Through shelter from frost, the winters are ren- 

 dered considerably less cold for them ; while shelter from 

 sun, assisted by evaporation, can make also the summers 

 cooler for plants thus treated, than it is to plants left in 

 the open air. And besides creating so many variations of 

 temperature, the gardener also largely controls the other 

 chief element of climate, by modifying almost at will the 

 humidity of earth and atmosphere, at any season, within 

 his frames and glass-houses. Even in ordinary gardens 

 the seasons are usually experienced under some favoring 

 conditions of shelter, and with the injurious extremes of 

 humidity prevented by drainage, and those of drought 

 relieved by artificial waterings. Outside these gardens, 

 again, there is the natural climate of Britain, with its 

 many local variations. 



All this is familiar enough. It is run over here in 

 brief descrii)tion, to impress the fact, that in this manner 

 there is really brought under botanical observation, and 

 condensed into small spaces of land, a vast amount of 

 floral and vegetal diversity, directly connected with and 

 dependant upon gi-eat diversities of climate. And the 

 demonstrated fact, that such differences are found service- 

 able or necessary in the cultivation of plants and crops, 

 shows that the climatal requirements of different species 

 of plants are widely different, in a more clear and con- 

 vincing manner than the same requirements and differ- 

 ences ever have been shown by the best treatises on 



VOL. IV. 3 p 



