Chap. XXIV. 



ACCLIMATISATION. 



305 



and vetches; but to this subject we shall immediately return 

 under acclimatisation. Annual plants sometimes become peren- 

 nial under a new climate, as I hear from Dr. Hooker is the case 

 with the stock and mignonette in Tasmania, On the other 

 hand, perennials sometimes become annuals, as with the Eicinus 

 in England, and as, according to Captain Mangles, with many 

 varieties of the heartsease. Von Berg 40 raised from seed of 

 Verhascum phcmicium, which is usually a biennial, both annual 

 and perennial varieties. Some deciduous bushes become ever- 

 green in hot countries. 41 Eice requires much water, but there is 

 one variety in India which can be grown without irrigation. 42 

 Certain varieties of the oat and of our other cereals are best fitted 

 for certain soils. 43 Endless similar facts could be given in the 

 animal and vegetable kingdoms. They are noticed here because 

 they illustrate analogous differences in closely allied natural 

 species, and because such changed habits of life, whether due to 

 use and disuse, or to the direct action of external conditions, 

 or to so-called spontaneous variation, would be apt to lead to 

 modifications of structure. 



Acclimatisation.— From the previous remarks we are naturally 

 led to the much disputed subject of acclimatisation. There are 

 two distinct questions: Do varieties descended from the same 

 species differ in their power of living under different climates? 

 And secondly, if they so differ, how have they become thus 

 adapted? We have seen that European dogs do not succeed 

 well m India, and it is asserted, 44 that no one has succeeded in 

 there keeping the Newfoundland long alive ; but then it may be 

 argued probably with truth, that these northern breeds are speci- 

 fically distinct from the native dogs which flourish in India. The 

 same remark may be made with respect to different breeds of 

 sheep, of which, according to Youatt, 4 * not one brought "from 

 a torrid climate lasts out the second year," in the Zoological 

 gardens. .But sheep are capable of some degree of acclimatisation, 

 for Merino sheep bred at the Cape of Good Hope have been found 



40 'Flora/1835, B.ii. p.504. 



41 Alph. De Candolle, ' Geograph 

 Bot./ torn. ii. p. 1078. 



42 Boyle, < Illustrations of the Botany 

 of the Himalaya/ p. 19. 



VOL. II. 



43 ' Gardener's Chronicle/ 1850, pp. 

 204, 219. 



44 Bev. B.Everest, 'Journal As. Soc. 

 of Bengal/ vol. iii. p. 19. 



4i> Youatt on Sheep, 1S38, p. 491. 



