ils and climates
even within the same country; thus Colonel Le Couteur[556] says, "It is
the suitableness of each sort to each soil that will enable the farmer
to pay his rent by sowing one variety, where he would be unable to do
so by attempting to grow another of a seemingly better sort." This may
be in part due to each kind becoming habituated to its conditions of
life, as Metzger has shown certainly occurs, but it is probably in main
part due to innate differences between the several varieties.

Much has been written on the deterioration of wheat; that the quality
of the flour, size of grain, time of flowering, and hardiness may be
modified by climate and soil, seems nearly certain; but that the whole
body of any one sub-variety ever becomes changed into another and
distinct sub-variety, there is no reason to believe. What apparently
does take place, according to Le Couteur,[557] 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 the natural crossing of distinct varieties the evidence
is conflicting, but preponderates against its frequent occurrence. Many
authors maintain that impregnation takes place in the closed flower,
but I am sure from my own observations that this is not the case, at
least with those varieties to which I have attended. But as I shall
have to discuss this subject in another work, it may be here 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.[558] It is an important fact, which we have recently
learnt from the admirable researches {317} of Heer,[559] 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 be shown that at the
earliest dawn of agriculture five kinds of wheat and three of bar