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Show 308 LAWS OF VARIATION. analogous case, namely, that in Sweden tobacco raised from home-grown seed ripens its seed a month sooner and is less liable to miscarry than plants raised from foreign seed. With the Vine, differently from the maize, the line of practical culture has retreated a little southward since the middle ages ; 60 but this seems due to commerce, including that of wine, being now freer or more easy. Nevertheless the fact of the vine not having spread northward shows that acclimatisation has made no progress during seveml centuries. 'rhere is, however, a marked difference in the constitution of the several varieties,some being hardy, whilst others, like the muscat of Alexandria, require a very high temperature to come to perfection. According to Labat,61 vines taken from France to the West Indies succeed with extreme difficulty, whilst those imported from Madeira, or the Canary I slands, thrive admirably. Gallesio gives a cmious account of the naturalisation of the Orange in Italy. During many centuries the sweet orange was propagated exclusively by grafts, and so often suffered from frosts that it req uircd protection. After the severe frost of 1709, and more especially after that of 1763, so many trees wore destroyed that seedlings from the sweet orange wore raised, and, to the surprise of the inhabitants, their fruit was found to he sweet. The trees thus raised were larger, more productive, and hardier than the former kinds; and seedlings are now continually raised. Hence Gallesio concludes that much more was effected for the naturalisation of the orange in Italy by the accidental production of new kinds dming a period of about sixty years, than had been effected hy grafting old varieties dming many agos.62 I may add that Risso 63 describes some Portuguese varieties of the orange as extremely sensitive to cold, and as much tenderer than certain other varieties. The peach was known to Theophrastus, 322 B.c.64 According to the authorities quoted by Dr. F. Rolle,65 it was tender when first introduced into Greece, and oven in the island of Rhodes only occasionally bore fruit. If this be conect, the peach, in spreading during the last two thousand years over the middle parts of Europe, must have become much hardier. At the present day different varieties differ much in hardiness : some French varieties will not succeed in England; and near Paris, the Pavie de B onneuil does not ripen its fruit till very late, even when grown on a wall; " it is, therefore, only fit for a very hot southern climate." 66 I will briefly give a few other cases. A variety of llf.1tgnolirt grandijlont, raised by M. Roy, withstands cold several degrees lower than that which any other variety can resist. With camellias there is much difference in hardiness. One particular variety of Noisette rose withstood the severe frost of 1860 "untouched and hale amidst a universal destruction of other 60 De Candolle, 'Geograph. Bot.,' p. 339. 61 ' Gard. Chronicle,' 1862, p. 235. 6'2 Gallesio, ' Teoria della Riproduzione Veg.,' 1816, p. 125; and 'Traite du Citrus,' 1811, p. 359. &3 ' Es,9ai sur l'Hist. des Orangers,' 1813, p. 20, &c. 64 Alph. De Candolle, 'Geograph. Bot.,' p. 882. 65 ' Ch. Darwin's Lehre von der Entstehung,' &c., 1862, s. 87. 66 Decaisne, quoted in ' Gard. Chro-nicle,' 1865, p. 271. • I I ACCLIMATISATION. 309 "Noisettes." In New York the "Irish yew is quite hardy, but the com" mon yew is liable to be cut down." I may add that there are varieties of the sweet potato (Convolvulus batatas) which are suited for warmer as well as for colder, climates.67 ' The plants as yet mentioned have been found capable of resisting an unusual degree of cold or heat, when fully grown. The following cases refer to plants whilst young. In a large bed of young Araucarias of the same age, growing close together a~d equally exposed, it was observed/8 after the unusually severe wmter of 1860-61, that, "in the midst of the dying, " numerous individuals remained on which the frost had abso" lut~ly made no kind of impression." Dr. Lindley, after alluditlg to this and other similar cases, remarks, ''Among "~he lessons which the late formidable winter has taught us, " Is that, even in their power of resisting cold, individuals of " the same species of plants are remarkably different." Near Salisbury, there was a sharp frost on the night of May 24th, 1836, and all the French beans (Pltaseolus vulgaris) in a bed were killed except about one in thirty, which completely escaped.69 On the same day of the month, but in the year 1864, there was a severe frost in Kent, and two rows of scarletrunners ( P. rnultijlorus) in my garden, containing 390 plants of the same age and equally exposed, were all blackened and killed except about a dozen plants. In an adjoining row of "Fulmer's dwarf bean" (P. vulgaris), one single plant escaped. A still more severe frost occurred four days afterwards, and of the dozen plants which had previously escaped only three survived; these were not taller or more vigorous than the other young plants, but they escaped completely, with not even the tips of their le~ves br?wned. It was impossible to behold these three plants, with thmr blackened, withered, and dead brethren all round t~em,. and not see at a. glance that they differed widely in constitutiOnal power of resisting frost. This work is not the proper place to show that wild plants 67 For the magnolia, see Louuon's ' Gard. lVIag.,' vol. xiii., 1R37, p. 21. For camellias and roses, see 'Gard. Chron.,' 1860, p. 384. For the yew, . 'Journal of Hort.,' March 3rd, 1863, p. 174. For sweet potatoes, see Col. von Siebold, in 'Gard. Chron.,' 1855, p. 822. 69 The Editor, ' Gard. Chrvn.,' 1861 p. 239. ' 69 Loudon's 'Gard. lVIag.,' vol. xii., 1836, p. 378 . |