rer we are to achieving our aim of
rendering a particular variation impossible or of making it dominant.

In addition to the individual variations of a species, more pronounced
fluctuations occur relatively rarely and sporadically which are spoken
of as "single variations," or if specially striking as abnormalities
or monstrosities. These forms have long attracted the attention of
morphologists; a large number of observations of this kind are given
in the handbooks of Masters (Masters, "Vegetable Teratology", London,
1869.) and Penzig (Penzig, "Pflanzen-Teratologie", Vols I. and II. Genua,
1890-94.) These variations, which used to be regarded as curiosities,
have now assumed considerable importance in connection with the causes
of form-development. They also possess special interest in relation to
the question of heredity, a subject which does not at present concern
us, as such deviations from normal development undoubtedly arise as
individual variations induced by the influence of environment.

Abnormal developments of all kinds in stems, leaves, and flowers, may
be produced by parasites, insects, or fungi. They may also be induced
by injury, as Blaringhem (Blaringhem, "Mutation et traumatismes", Paris,
1907.) has more particularly demonstrated, which, by cutting away the
leading shoots of branches in an early stage of development, caused
fasciation, torsion, anomalous flowers, etc. The experiments of
Blaringhem point to the probability that disturbances in the conditions
of food-supply consequent on injury are the cause of the production of
monstrosities. This is certainly the case in my experiments with species
of Sempervivum (Klebs, "Kunstliche Metamorphosen", Stuttgart, 1906.);
individuals, which at first formed normal flowers, produced a great
variety of abnormalities as the result of changes in nutrition, we
may call to mind the fact that the formation of inflorescences occurs
normally when a vigorous production of organic compounds, such as
starch, sugar, etc. follows a diminution in the supply of mineral
salts. On the other hand, the development of inflorescences is entirely
suppressed if, at a suitable moment before the actual foundations have
been laid, water and mineral salts are supplied to the roots. If, during
the week when the inflorescence has just been laid down and is growing
very slowly, the supply of water and salts is increased, the internal
conditions of the cells are essentially changed. At a lat