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Show 310 LAWS OF VARIATIO~. CHAP. XXIV. of the same species, naturally growing at different altitu<leti or under different latitudes, become to a certain extent acclimatised, as is proved by the different behaviour of their seedlings when raised in England. In my 'Origin of Species' I have alluded to some cases, and I could add others. One instance must suffice: Mr. Grigor, of Forres/0 states that seedlings of the Scotch fir ( Pin'US sylvestris ), raised from seed from the Continent and from the forests of Scotland, differ much. "The difference is perceptible in one-year-old, and more " so in two-year-old seedlings; but the effects of the winter on "the second year's growth almost uniformly makes those from " the Continent quite brown, and so damaged, that by the month " of March they are quite unsaleablc, while the plants from the '' native Scotch pine, under the same treatment, and standing " alongside, although considerably shorter, are rather stouter and " quite green, so that the beds of the one can be known from the "other when seen from the distance of a mile." Closely similar facts have been observed with seedling larches. Hardy varieties would alone be valued or noticed in Europe; whilst tender varieties, requiring more warmth, would genemlly be neglected; but such occasionally arise. Thus Loudon 71 describes a Cornish variety of tho elm which is almost an evergreen, and of whieh tho shoots are often killed by the autumnal frosts, so that its timber is of little value. Horticulturists know that some varieties aro much more tender than others : thus all the varieties of the broccoli are more tender than cabbages; but there is much difference in this respect in the sub-varieties of the broccoli; the pink and purple kinds are a little hardier than the white Cape broccoli, " but they are not to be depended on after the thermometer "falls below 24? Fahr.:" the Walcheren broccoli is less tender than tho Cape, anJ. there are several varieties which will stand much severer cold than tho Walcheren.72 Cauliflowers seed more freely in India than cabbages. 73 To give one instance with flowers: eleven plants raised from a hollyhock, called. tho Queen of the Whitts/4 were found. to be much more tender than various other seedlings. It may be presumed that all tender varieties would succeed better under a climate warmer than ours. With fruit-trees, it is well known that certain varieties, for instance of the peach, stand forcing in a hot-house better than others; and this shows 70 ' Gardener's Chron.,' 1865, p. 699. i 1 'Arboretum ot Fruticeturn,' vol. iii. p. 1376. 72 Mr. Robson, in 'Journal of Horticulture,' 1861, p. 23. 73 Dr. Bonavia, 'Report of tho Agri.Hort. Roc. of Ouclh,' l8G6. 74 'Cottage Gardener,' 1860, April, 24th, p. 57. CUAP. XXIV. ACCLIMATISATION. 311 either pliabilit.y of organisation or some constitutional difference. The same individual cherry-tree, when forced, has been observed during successive years gradually to change its period of vcgctation.76 Few pelargoniums can resist the heat of a stove, but .Alblt multiflora will, as a most skilful gardener asserts, "stand pine-apple top and bottom heat the whole "winter, without looking any more drawn than if it had stood in a com" mon greenhouse; and Blanche Fleur- seems as if it had been made on " purpose for growing in winter, like many bulbs, and to rest all summer." 7 6 There can hardly be a doubt that the Alba multiflora pelargonium must have a widely different constitution from that of most other varieties of this plant; it would probably withstand even an equatorial climate. We have seen that according to Labat the vine and wheat require acclimatisation in order to succeed in the West Indies. Similar facts have been observed at Madras: " two parcels of mignonette-seed, one direct "from Europe, the other saved at Bangalore (of which the mean tempera" ture is much below that of Madras) were sown at the same time : they both " vegetated equally favourably, but the former all died off a few days after " they appeared above ground; the latter still survive, and are vigorous " healthy plants." So again, "turnip and carrot seed saved at Hyderabad " arc found to answer better at Madras than seed from Em·ope or from the " Cape of Good Hope." 77 Mr. J. Scott, of the Calcutta Botanic Gardens informs me that seeds of the sweet-pea (Lathyrus odoratus) imported fl'o~ England produce plants, with thick, rigid stems and small leaves, which rarely blossom and never yield seed; plants raised fl'om French seed blossom sparingly, but all the flowers are sterile; on the other hand, plants raised from sweetrpeas grown near Darjeeling in Upper India, but originally derived from England, can be successfully cultivated on the plains of India; for they flower and seed profusely, and their stems are lax and scandent. In some of the foregoing cases, as Dr. Hooker has remarked to me, the greater success may perhaps be attributed to the seeds having been more fully ripened under a more favourable climate· but this view can hardly be extended to so many cases, including plants: which, from being cultivated under a climate hotter than their native one, become fitted for a still hotter climate. We may therefore safely conclude that plants can to a certn,in extent become accustomed to a climate either hotter or colder than their own; although these latter cases have been more frequently observed. We will now consider the means by which acclimatisation may be effected, namely, through the spontaneous appearance of. varieties having ~ different constitution, and through the effects of use or habit. In regard to the fu·st process, there is no evidence that a change in the constitution of the off- 75 'Gardener's Chronicle,' 1841, p. 291. i6 Mr. Beaton, in • Cottage Gardener,' March 20th, 1860, p. 377. Queen Mab will also stand stove heat, see ' Gard. Chronicle,' 1845, p. 226. 11 ' .Gardener's Chronicle,' 1841 p 439. ' |