aces which under certain definite conditions
lose their colour or their virulence. Among the phanerogams the
investigations of Schubler on cereals afford parallel cases, in which
the influence of a northern climate produces individuals which ripen
their seeds early; these seeds produce plants which seed early in
southern countries. Analogous results were obtained by Cieslar in his
experiments; seeds of conifers from the Alps when planted in the plains
produced plants of slow growth and small diameter.

All these observations are of considerable interest theoretically; they
show that the action of environment certainly induces such internal
changes, and that these are transmitted to the next generation. But as
regards the main question, whether constant races may be obtained by
this means, the experiments cannot as yet supply a definite answer. In
phanerogams, the influence very soon dies out in succeeding generations;
in the case of bacteria, in which it is only a question of the loss of
a character it is relatively easy for this to reappear. It is not
impossible, that in all such cases there is a material hanging-on of
certain internal conditions, in consequence of which the modification
of the character persists for a time in the descendants, although the
original external conditions are no longer present.

Thus a slow dying-out of the effect of a stimulus was seen in my
experiments on Veronica chamaedrys. (Klebs, "Kunstliche Metamorphosen",
Stuttgart, 1906, page 132.) During the cultivation of an artificially
modified inflorescence I obtained a race showing modifications in
different directions, among which twisting was especially conspicuous.
This plant, however, does not behave as the twisted race of Dipsacus
isolated by de Vries (de Vries, "Mutationstheorie", Vol. II. Leipzig,
1903, page 573.), which produced each year a definite percentage of
twisted individuals. In the vegetative reproduction of this Veronica the
torsion appeared in the first, also in the second and third year, but
with diminishing intensity. In spite of good cultivation this character
has apparently now disappeared; it disappeared still more quickly in
seedlings. In another character of the same Veronica chamaedrys the
influence of the environment was stronger. The transformation of the
inflorescences to foliage-shoots formed the starting-point; it occurred
only under narrowly defined conditions, namely on cultivation as a
cutting in moist air