Chap. XXIV. ACCLIMATISATION. 297 



summer here is not hot enough. Fruit-trees have also originated 

 in Europe with different constitutions, but they are not much 

 noticed, because nurserymen here do not supply wide areas. The 

 Forelle pear flowers early, and when the flowers have just set, and 

 this is the critical period, they have been observed, both in France 

 and England, to withstand with complete impunity a frost of 18° 

 and even 14° Fahr., which killed the flowers, whether fully expanded 

 or in bud, of all other kinds of pears. 50 This power in the flower of 

 resisting cold and afterwards producing fruit does not invariably 

 depend, as we know on good authority, 51 on general constitutional 

 vigour. In proceeding northward, the number of varieties which 

 are found capable of resisting 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. 52 Near 

 Moscow, Prince Troubetzkoy planted for experiment in the open 

 ground several varieties of the pear, but one alone, the Poire san> 

 Pepins, withstood the cold of winter. 53 We thus see that our fruit- 

 trees, like distinct species of the same genus, certainly differ from 

 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 culti- 

 " vation in Scotland ; " 5i but the failure in this case is at first only 

 in the quantity, though ultimately in the quality, of the grain 

 produced. The Eev. M. J. 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 furnished with only two or three miserable seeds, while 

 " West Indian seed by its side yielded an enormous harvest." 5(i 

 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 if 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 proceed- 

 ing northward, the varieties cultivated in each zone produce their 



50 < Gard. Chronicle,' 1860, p. 938. p. 7. 



Remarks by Editor and quotation 54 ' Gard. Chronicle,' 1851, p. 39(3. 



from Decaisne. 55 Ibid., 1862, p. 235. 



51 J. de Jonghe, of Brussels, in 56 On the authority of Labat, 

 * Gard. Chronicle,' 1857, p. 612. quoted in 'Gard. Chron.,' 1862, p. 



52 Ch. Martius, 'Voyage Bot. Cotes 235. 



Sept. de la Norvege,' p. 26. « MM.Edwards and Colin, < Annal 



53 ' Journal de l'Acad. Hort. de des Sc. Nat.,' 2nd series, Bot., torn, v 

 Gand,' quoted in ' Gard. Chron.,' 1859, p. 22. 



