Now, all these circumstances seem to point to a similarity in essential structure, and a uniformity of habit somewhat remarkable in plants which at first sight would strike one as being so different; but as these differences between _Ægilops_ and any variety of wheat are often all scarcely greater than is to be met with on contrasting two known varieties of wheat, we may agree in concluding that the evidence warrants the assumption that wheat, as a cultivated cereal, has been derived from _Ægilops_. If, then, we view the wheat plant as a derivative, we shall be at no loss in understanding how the vast number of varieties have been brought about—varieties applicable, too, to a wide range of climatal conditions; and the ease with which new forms can be brought about by hybridization and selection is a matter of importance, because older varieties, too often repeated, are apt to degenerate both in quality of grain and quantity of crop. But when we speak of acclimatizing wheat, we think it would be excessively difficult to make any existing form grow well in a climate not congenial to it, though it might be easy to arrive at a new variety possessing some desired quality. We believe, however, that it is not difficult to alter a climate to suit a sort, and, in all probability, this at the present day much-used term of “acclimatization” simply means no more than making our cultivation and climate accord as nearly as possible to the habits of the plant or animal to be entertained under new conditions. Thus, when we see the finer white wheats growing good crops on farms where such would have been impossible a few years ago, we are hardly to conclude that we have at length got this more delicate sort to become more hardy; but the climate has been ameliorated by draining and better cultivation. We distinctly recollect when the lias clays of the Vale of Gloucester could scarcely be made to grow a good crop of even the hardier sorts of red wheat, the common cone being the sort generally grown. This was succeeded by many sorts of red wheat, and now only the best-cultivated farms produce white wheats. These, however, are facts which will be more strongly brought out when we consider the subject of cultivation; for the present we would be content with the expression of a belief that wheat, as a cereal grain, is derived by cultivation from a wild grass, and it is due to the effects of cultivation that we have so many sorts, with such variable adaptability. CHAPTER XXVI. THE WILD OAT AS THE ORIGIN OF THE CULTIVATED VARIETIES.