Flax is another instance. It was already cultivated, or at least made
use of during the period of the lake-dwellers, but at that time it was a
species referred to as _Linum angustifolium_, and not the _Linum
usitatissimum_, which is our present day flax. There are now many
subspecies, elementary species, and varieties under cultivation. The
oldest of them is known as the "springing flax," in opposition to the
ordinary "threshing flax." It has capsules which open of themselves, in
order to disseminate the seeds, while the ordinary heads of the [81]
flax remain closed until the seeds are liberated by threshing. It seems
probable that the first form or _Linum crepitans_ might thrive in the
wild state as well as any other plant, while in the common species those
qualities are lacking which are required for a normal dissemination of
the seeds. White or blue flowers, high or dwarf stems, more or less
branching at the base and sundry other qualities distinguish the
varieties, aside from the special industrial difference of the fibres.
Even the life-history varies from annual and biennial, to perennial.
It would take us too long to consider other instances. It is well known
that corn, though considered as a single botanical species, is
represented by different subspecies and varieties in nearly every region
in which it is grown.
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