32 On producing New and Early Fruits. 



their habits to any climate in which art or accident places 

 them. 



But the influence of climate on the habits of plants, will 

 depend less on the aggregate quantity of heat in each cli- 

 mate, than on the distribution of it in the different seasons of 

 the year. The aggregate temperature of England, and of 

 those parts of the Russian Empire, that are under the same 

 parallels of latitude, probably does not differ very considerably; 

 but, in the latter, the summers are extremely hot, and the 

 winters intensely cold ; and the changes of temperature be- 

 tween the different seasons are sudden and violent. In the 

 spring great degrees of heat suddenly operate on plants which 

 have bex^n long exposed to intense cold, and in which excita- 

 bility has accumulated during a long period of almost total 

 inaction : and the progress of vegetation is in consequence 

 extremely rapid. In the climate of England, the spring, on 

 the contrary, advances with slow and irregular steps, and 

 only very moderate and slowly-increasing degrees of heat act 

 on plants in which the powers of life have scarcely in any 

 period of the preceding winter been totally inactive. The 

 Crab is a native of both countries, and has adapted alike its 

 habits to both ; the Siberian variety introduced into the cli- 

 mate of England, retains its habits, expands its leaves, and 

 blossoms on the first approach of spring, and vegetates strongly 

 in the same temperature in which the native Crab scarcely 

 shows signs of life ; and its fruit acquires a degree of matu- 

 rity, even in the early part of an unfavourable season, which 

 our native Crab is rarely, or never seen to attain. 



Similar causes are productive of similar effects on the 

 habits of cultivated annual plants ; but these appear most 



