Chap. XXIV. 



ACCLIMATISATION. 



307 



In proceeding northward, the number of varieties which are enabled to 

 resist the climate rapidly decreases, as may be seen in the list of the 

 varieties of the cherry, apple, and pear, which can be cultivated in the 

 neighbourhood of Stockholm." Near Moscow, Prince Troubetzkoy planted 

 for experiment m the open ground several varieties of the pear, but one 

 alone the Poire sans Pepins, withstood the cold of winter." We thus 

 see that our fruit-trees, like distinct species of the same genus, certainly 

 diner irom each other in their constitutional adaptation to different 

 climates. 



With the varieties of many plants, the adaptation to climate is often very 

 close. Thus it has been proved by repeated trials "that few if any of the 



English varieties of wheat are adapted for cultivation in Scotland ; " 54 but 

 the failure m this case is at first only in the quantity, though ultimately in 

 the quality, of the grain produced. The Eev. J. M. Berkeley sowed wheat- 

 seed from India, and got « the most meagre ears," on land which would 

 certainly have yielded a good crop from English wheat. 55 In these cases 

 varieties have been carried from a warmer to a cooler climate; in the 

 reverse case, as "when wheat was imported directly from France into the 

 ' West Indian Islands, it produced either wholly barren spikes or fur- 

 " m Sh f d ?I ith ml ? two or thr ee miserable seeds, while West Indian seed 



by its side yielded an enormous harvest." « Here is another case of close 

 adaptation to a slightly cooler climate; a kind of wheat which in England 

 may be used indifferently either as a winter or summer variety when 

 sown under the warmer climate of Grignan, in France, behaved exactly 

 as it it had been a true winter wheat. 57 



Botanists believe that all the varieties of maize belong to the same 

 species; and we have seen that in North America, in proceeding north- 

 ward, the varieties cultivated in each zone produce their flowers and 

 ripen their seed within shorter and shorter periods. So that the tall 

 slowly maturing southern varieties do not succeed in New England, and 

 the New English varieties do not succeed in Canada. I have not met with 

 any statement that the southern varieties are actually injured or killed bv 

 a degree of cold which the northern varieties withstand with impunity 

 though this is probable; but the production of early flowering and early 

 seedmg varieties deserves to be considered as one form of accusation 



SSSr Lff^T .1 P ° SS i ble ' aCC ° rding t0 Kalm > t0 ™ lti ™te ^ize 

 further and further northwards in America. In Europe, also, as we learn 



Xndersmcrth 6 fTft^ * ^^ the ^ * "^ 

 M^oX7 l* he ^\^™yM*J leagues north of its former 

 boundary. On the authority of the great Linnams - I may quote an 





52 Oh. Martius, 'Voyage Bot. Cotes 

 Sept. de la Norvege,' p. 26. 



53 ' Journal de T Acad. Hort. de Grand,' 

 quoted in ' Gard. Chron.,' 1859, p. 7. 



54 ' Gard. Chronicle,' 1851, p. 396] 



55 Idem., 1862, p. 235. 



56 On the authority of Labat, quoted 

 in 'Gard. Chron.,' 1862, p. 235. 



57 MM. Edwards and Colin, * Annal. 

 des Sc. Nat.,' 2ndseries,Bot.,tom. v.p.22. 



58 Geograph. Bot.,' p. 337. 



59 'Swedish Acts,' Eng. translat., 

 1739-40, vol. i. Kalm, in his ' Travels,' 

 vol. ii. p. 166 ? gives an analogous case 

 with cotton-plants raised in New Jersey 

 from Carolina seed. 



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