Most of them
occupy one or more departments of France, and in Holland two of them are
spread over several provinces. An important number are native in the
centre of Europe, and from the vicinity of Lyons, Jordan succeeded in
establishing about fifty elementary [50] species in his garden. In this
region they are crowded together and not rarely two or even more quite
distinct forms are observed to grow side by side on the same spot.
Farther away from this center they are more widely dispersed, each
holding its own in its habitat. In all, Jordan has distinguished about
two hundred species of _Draba verna_ from Europe and western Asia.
Subsequent authors have added new types to the already existing number
from time to time.
The constancy of these elementary species is directly proven by the
experiments quoted above, and moreover it may be deduced from the
uniformity of each type within its own domain. These are so large that
most of the localities are practically isolated from one another, and
must have been so for centuries. If the types were slowly changing such
localities would often, though of course not always, exhibit slighter
differences, and on the geographic limits of neighboring species
intermediates would be found. Such however, are not on record. Hence the
elementary species must be regarded as old and constant types.
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