304: LAWS OF VARIATION. Chap. XXIV. 



in Northern Europe, are comparatively more precocious, and 

 need much less heat for maturing their fruit, than the 

 varieties of the same species recently brought from tropical 

 regions. In the reciprocal conversion of summer and winter 

 wheat, barley, and vetches into each other, habit produces 

 a marked effect in the course of a very few generations. 

 The same thing apparently occurs with the varieties of 

 maize, which, when carried from the Southern States of 

 America, or into Germany, soon became accustomed to their 

 new homes. With vine-plants taken to the West Indies from 

 Madeira, which are said to succeed better than plants brought 

 directlj'- from France, we have some degree of acclimatisation 

 in the individual, independently of the production of new 

 varieties by seed. 



The common experience of agriculturists is of some value, 

 and they often advise persons to be cautious in trying the 

 productions of one country in another. The ancient agri- 

 cultural writers of China recommend the preservation and 

 cultivation of the varieties peculiar to each country. During 

 the classical period. Columella wrote, " Vernaculum pecus 

 " peregrine longe preestantius est.""^ 



I am aware that the attempt to acclimatise either animals 

 or plants has been called a vain chimera. No doubt the 

 attempt in most cases deserves to be thus called, if made in- 

 dependently of the production of new varieties endowed with 

 a different constitution. With plants propagated by buds, 

 habit rarely produces any effect ; it apparently acts only 

 through successive seminal generations. The laurel, haj^ 

 laurestinus, &c., and the Jerusalem artichoke, which are pro- 

 pagated by cuttings or tubers, are probably now as tender in 

 England as when first introduced ; and this appears to be the 

 case with the potato, which until recently was seldom mul- 

 tiplied by seed. With plants propagated by seed, and with 

 animals, there will be little or no acclimatisation unless the 

 hardier individuals are either intentionally or unconsciously 

 preserved. The kidney-bean has often been advanced as an 



^® For China, see ' Memoire sur ' Journal de Physique,' torn, xxiv., 

 les Chiuois,' torn, xi., 1786, p. 60. 178J-, 

 Columella is quoted hj Carljer, in 



