OBSERVABLE PROPERTIES OF EACH SPECIES 23 



the characteristics of torsus. One might think that a very re- 

 markable variation has been brought about by cultivation, 

 the more so because the twisted stems would be hereditary by 

 further cultivation under favourable conditions. Many horti- 

 cultural species which have been found in a seed-plot have 

 probably a similar origin. In reality, in such cases, no new 

 form is produced, the property of plasticity is not modified, but 

 unusual external causes have brought about unusual reactions 

 of the living mixture, which are no longer observed as soon as the 

 unusual causes have ceased to prevail. 



Among the subspecies (races) which have been investigated 

 by H. DE VRIES in the same way as D. silv. torsus, with 

 similar results, several subspecies with fasciated stems, ascidi- 

 form leaves, three cotyledons, etc., may be mentioned. 



§ 28.— VARIATION UNDER CULTIVATION {continued). 

 REMARKS. — I think that the great majority of the examples 

 of variation under cultivation, which are mentioned in bio- 

 logical hterature may be brought into the four following 

 groups : — 



(i) Greater variation under cultivation is simply a delusive 

 appearance, a consequence of incomplete information about 

 plasticity in the state of nature (§§ 23, 24) . 



(2) Certain properties which are- always or almost always 

 latent under natural conditions become observable under the 

 unusual conditions which prevail in a garden (§ 25). 



(3) When the cultivated material is regarded as being mono- 

 typic, although it is complex, the properties of certain of its 

 monotypic components may become visible under cultivation 

 because certain specimens are hybrids (§ 26). 



(4) When the cultivated material is looked upon as being 

 monotypic, although it is complex, the properties of certain of 

 its monot5^ic components which are latent or very rarely 

 observable in the state of nature may become visible under 

 the new conditions which prevail imder cultivation (§ 27). 



It is easily realized that several of the possibiUties aUuded to 

 may coexist and bring about various and intricate combina- 

 tions in one group of cultivated plants. 



In short, it seems as if our ignorance about complexity and 

 plasticity among plants and animals under natural conditions 

 were the origin of the belief that variability is increased by 

 cultivation or domestication. (A restriction is made in note 2 

 on p. 20 ; see further the present paragraph.) 



Botanists and zoologists who are collectors may make much 

 progress by observing and collecting specimens which exhibit 

 unusual properties, inscribing on the labels exact information 

 about the conditions of existence and about certain properties 



