Chap. XXIV. ACCLIMATISATION. 313 



hear that Merino sheep, bred during no great number of genera- 

 tions at the Cape of Good Hope — that some European plants 

 raised during only a few generations in the cooler parts of 

 India, withstand the hotter parts of that country much better 

 than the sheep or seeds imported directly from England, we 

 must attribute some influence to habit. We are led to the 

 same conclusion when we hear from Naudin 78 that the races of 

 melons, squashes, and gourds, which have long been cultivated 

 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 ap- 

 parently occurs with the varieties of maize, which, when carried 

 from the Southern to the Northern States of America, or into 

 Germany, soon become accustomed to their new homes. With 

 vine-plants taken to the West Indies from Madeira, which are 

 said to succeed better than plants brought directly from France, 

 we have some degree of acclimatisation in the individual, inde- 

 pendently 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 in one 

 country the productions of another. The ancient agricultural 

 writers of China recommend the preservation and cultivation 

 of the varieties peculiar to each country. During the classical 

 period, Columella wrote, " Vernaculum pecus peregrino longe 

 " prsestantius est." 79 



I am aware that the attempt to acclimatise either animals or 

 plants has been called a vain chimaera. No doubt the attempt 

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

 ently of the production of new varieties endowed with a dif- 

 ferent constitution. Habit, however much prolonged, rarely 

 produces any effect on a plant propagated by buds; it ap- 

 parently acts only through successive seminal generations. 



< 8 Quoted by Asa Gray, in ' Am. Chinois,' torn. xi. 1786, p. 60. Columella 

 . Journ. of Soi.,' 2nd series, Jan. 1865, is qilo ted by Carlier, in < Journal de 



£• 106 - Physique,' torn. xxiv. 1784. 



/9 For China, see 'Memoire sur les 



