Production of Constant Races 243 
found in some races which under certain definite conditions lose 
their colour or their virulence. Among the phanerogams the in- 
vestigations of Schiibler 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 experi- 
ments; 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 gene- 
ration. 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'. During the cultivation of 
an artificially modified inflorescence I obtained a race showing modi- 
fications 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’, which produced each year a 
definite percentage of twisted individuals. In the vegetative repro- 
duction 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 in- 
florescences to foliage-shoots formed the starting-point; it occurred 
only under narrowly defined conditions, namely on cultivation as a 
cutting in moist air and on removal of all other leaf-buds. In the 
majority (j#;) of the plants obtained from the transformed shoots, 
the modification appeared in the following year without any inter- 
ference. Of the three plants which were under observation several 
years the first lost the character in a short time, while the two others 
1 Klebs, Kiinstliche Metamorphosen, Stuttgart, 1906, p. 132. 
2 de Vries, Mutationstheorie, Vol. u. Leipzig, 1903, p, 573. 
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