Monstrosities 237 
ticular form or number, and are able to reproduce it by experiment, 
the nearer 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 pro- 
nounced fluctuations occur relatively rarely and sporadically which 
are spoken of as “single variations,” or if specially striking as ab- 
normalities 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: and Penzig?. 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 environ- 
ment. 
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? 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‘ ; indi- 
viduals, 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. Ata later 
stage, after the elongation of the inflorescence, rosettes of leaves are 
produced instead of flowers, and structures intermediate between the 
two kinds of organs; a number of peculiar plant-forms are thus 
obtained®. Abnormalities in the greatest variety are produced in 
1 Masters, Vegetable Teratology, London, 1869. 
2 Penzig, Pflanzen-Teratologie, Vols. 1. and 1. Genua, 1890—94. 
3 Blaringhem, Mutation et traumatismes, Paris, 1907. 
« Klebs, Kiinstliche Metamorphosen, Stuttgart, 1906. 
5 Cf, Lotsy, Vorlesungen tlber Deszendenztheorien, Vol. 1. pl. 3, Jena, 1908. 
