sensibly changed by cultivation in South America; for, according to
Tschudi, the ears of this grain found in old Peruvian tombs belong to
varieties not now known in Peru.--Travels in Peru, chap. vii. See
important observations in Schubeler, Die Pflanzenwelt Norwegans
(Allgemeiner Theil), Christinania, 1873, 77 and following pp.] Even if
we suppose an identity of species, of race, and of habit to be
established between a given ancient and modern plant, the negative fact
that the latter will not grow now where it flourished two thousand years
ago does not in all cases prove a change of climate. The same result
might follow from the exhaustion of the soil, [Footnote: The cultivation
of madder is said to have been introduced into Europe by an Oriental in
the year 1765, and it was first planted in the neighborhood of Avignon.
Of course, it has been grown in that district for less than a century;
but upon soils where it has been a frequent crop, it is already losing
much of its coloring properties.--Lavergne, Economic Rurale de la
France, pp. 250-201.

I believe there is no doubt that the cultivation of madder in the
vicinity of Avignon is of recent introduction; but it is certain that it
was grown by the ancient Romans, and throughout nearly all Europe in the
middle ages. The madder brought from Persia to France, may belong to a
different species, or at least variety.] or from a change in the
quantity of moisture it habitually contains. After a district of country
has been completely or even partially cleared of its forest growth, and
brought under cultivation, the drying of the soil, under favorable
circumstances, goes on for generations, perhaps for ages. [Footnote: In
many parts of New England there are tracts, many square miles in extent
and presenting all varieties of surface and exposure, which were
partially cleared sixty or seventy years ago, and where little or no
change in the proportion of cultivated ground, pasturage, and woodland