of selection is so important, yet the little which
man has effected, by incessant efforts[562] during thousands of years, in
rendering the plants more productive or the grains more nutritious than
they were in the time of the old Egyptians, would seem to speak strongly
against its efficacy. But we must not forget that at each successive period
the state of agriculture and the quantity of manure supplied to the land
will have determined the maximum degree of productiveness; for it would be
impossible to cultivate a highly productive variety, unless the land
contained a sufficient supply of the necessary chemical elements.

We now know that man was sufficiently civilized to cultivate the ground at
an immensely remote period; so that wheat might have been improved long ago
up to that standard of excellence which was possible under the then
existing state of agriculture. One small class of facts supports this view
of the slow and gradual improvement of our cereals. In the most ancient
lake-habitations of Switzerland, when men employed only flint-tools, the
most extensively cultivated wheat was a peculiar kind, with remarkably
small ears and grains.[563] "Whilst the grains of the modern forms are in
section from seven to eight millimetres in length, the larger grains from
the lake-habitations are six, seldom seven, and the smaller ones only four.
The ear is thus much narrower, and the spikelets stand out more
horizontally, than in our present forms." So again with barley, the most
ancient and most extensively cultivated kind had small ears, and the grains
{319} were "smaller, shorter, and nearer to each other, than in that now
grown; without the husk they were 21/2 lines long, and scarcely 11/2 broad,
whilst those now grown have a length of three lines, and almost the same in
breadth."[564] These small-grained varieties of wheat and barley are
believed by Heer to be the parent-forms of certain existing allied
varieties, which have supplanted their early progenitors.

Heer gives an interesting account of the first appearance and final
disappearance of the several plants which were cultivated in greater or
less abundance in Switzerland during former successive periods, and which
generally differed more or less from our existing varieties. The peculiar
small-eared and small-grained wheat, already alluded to, was the commonest
kind during the Stone period; it lasted down to the Helvetico-Roman age,
and then became extinct. A sec