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. AVe 

 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 do^vn 

 and is growing very slowly, the supply of water and salts is increased, 

 the internal conditions of the cells are essentially changed. At a 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 Tcratolofjij, London, 18G9. 



* Tenzig, Pjlanzen-Teralologie, Vols. i. and ii. Genua, 1890—94. 



* Blaringhem, Mutation et traumatismes, Paris, 1907. 



* Klebs, K'dngtUche Melaniorphoncn, Stuttgart, 1906. 



'' Cf. LotHy, Vorlesungcn iiber Dcszendenzllteoiien, Vol. ii. pi. 3, Jena, 1903. 



