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Show 316 CEREAL PLANTS. CHAP. IX. country was useless for corn crops. It is notorious that tho proportion of gluten dillcrs much under different climates. Tho weight of tho grain iR also quickly nflcctcd by climate: Loisclcur-Dcslongchamps 37 sowed ncar Paris 54 varictic. ·, obtained from the South of Fr.mco and from the Black Sea, and 52 of these yielded seed from 10 to 40 per cent. heavier than tho parent-seed. IIo then sent these heavier grains back to tho South of France, but there they immediately yielded lighter seed. .All those who have closely attended to tho subject insist on tho close adaptation of numerous varieties of wheat to various soils and climates oven within the same country; thus Colonel Lo Coutcur ~" says, "It is tho suitableness of each sort to each soil tbat will enable tho farmer to pay his rent by sowing one variety, whore he would be unable to do so by attempting to grow another of a seemingly better sort." This may be in part clue to each kind becoming habituated to its conditions of life, as Metzger bas shown certainly occms, but it is probably in main part duo to innate differences between tho several varieties. Much has been written on tho deterioration of wheat; that tho quality of tho flom, size of grain, time of flowering, and hardiness may be modified by climate and soil, seems nearly certain; but that tho whole bucly of any one sub-variety over becomes changed into another and distinct subvariety, thoro is no reason to believe. What apparently does take place, according to Lo Coutcm}9 is, that some one sub-variety out of the many which may always be detected in the same field is more prolific than the others, and gradually supplants the variety which was first sown. With respect to tho natural crossing of distinct varieties tho evidence is conflicting, but preponderates against its frequent occmrencc. 1\fany authors maintain that impregnation takes place in tho closed flower, but I am sure from my own observations that this is not tho case, at least with those varieties to which I have attended. But as I shall have to discuss tllis subject in another work, it may be hero passed over. In conclusion, all authors admit that numerous varieties of wheat have arisen; but their differences are unimportant, unless, indeed, some of the so-called species are ranked as varieties. Those who believe that from four to seven wild species of Triticum originally existed in nearly the same condition as at present, rest their belief chiefly on the great antiquity of the several . forms.40 It is an important fact, which we have recently learnt from the admirable researches 37 'Cercales,' part ii. pp. 179- 183. 38 'On tho Varieties of Wheat,' Introduet., p. vii. See Marshall, 1 Rural Econ. of Yorkshire,' vol. ii. p. 9. With r espect to similar cases of adaptation in the varieties of oats, see some interesting papers in tho 'Gardener's Cluon. and Agricult. Gazette,' 1850, pp. 204, 219. ~9 • On tho Vurict ies of Wheat,' p. 5!). Mr. Sheriif, and a higher authority cannot be given (' Gard. Chron. and Agricult. Gawtto,' 1862, p. 963), says, "I have never seen grain which has either been improved or degenerated by cultivation, so as to convey the change to tho succeeding crop." •o Alph. Do Candolle, 1 Gcograp1l. Bot.,' p. D30. CIIAP. IX. WIIEAT. 317 {)f I-Ieer 41 that the inhabitants of Switzerland, even so early as the 'Neolithic period, cultivated no less than ten cereal plants, namely, five kinds of wheat, of which at least four are commonly looked at as distinct species, three kinds of barley, a panicum, and a setaria. If it could bo shown that at the earliest dawn of a<Yriculture five kinds of wheat and three of barley had been c~ltivated, we should of course be compelled to look at these forms as distinct species. But, as Heer has remarked, agriculture even at the period of the lake-habitations had already made considerable progress; for, besides the ten cereals, peas, poppies, flax, and apparently apples, were cultivated. It may also be inferred, from one variety of wheat being the socalled Egyptian, and from what is known of the native country of the panicum and setaria, as well as from the nature of the weeds which then grew mingled with the crops, that the lakeinhabitants either still kept up commercial intercourse with some southern people or had originally proceeded as colonists from the South. · Loiseleur-Deslongchamps 42 has argued that, if our cereal plants bad been greatly modified by cultivation, the weeds which habitually grow mingled with them would have been equally modified. But this argument shows how completely the principle of selection has been overlooked. That such weeds have not varied, or at least do not vary now in any extreme degree, is the opinion of Mr. H. C. Watson and Professor Asa Gray, as they inform me; but who will pretend to say that they do not vary as much as the individual plants of the same sub-variety of wheat? We have already seen that pure varieties of wheat, cultivated in the same field, offer many slight variations, which can be selected and separately propagated; and that occasionally more strongly pronounced variations appear, which, as Mr. Sheriff bas proved, are well worthy of extensive cultivation. Not until equal attention be paid to the variability and selection of weeds, can the argument from their constancy under unintentional culture be of any value. In accordance with the principles of selection we -can understand how it is that in the several cultivated varieties of wheat the organs of vegetation differ so little ; for if a plant 41 'Pflanzen der Pfahlbauten,' 1866. •2 • Les Cereales,' p. 94. |