in Hybridisation 369 



experiments, since it is probable that in this way we might 

 learn the significance of the extraordinary variety in the 

 colouring of our ornamental flowers. 



So far, little at present is known with certainty beyond 

 the fact that the colour of the flowers in most ornamental 

 plants is an extremely variable character. The opinion 

 has often been expressed that the stability of the species 

 is greatly disturbed or entirely upset by cultivation, and 

 consequently there is an inclination to regard the develop- 

 ment of cultivated forms as a matter of chance devoid of 

 rules ; the colouring of ornamental plants is indeed usually 

 cited as an example of great instability. It is, however, 

 not clear why the simple transference into garden soil 

 should result in such a thorough and persistent revolution 

 in the plant organism. No one will seriously maintain 

 that in the open country the development of plants is ruled 

 by other laws than in the garden bed. Here, as there, 

 changes of type must take place if the conditions of life be 

 altered, and the species possesses the capacity of fitting 

 itself to its new environment. It is willingly granted that 

 by cultivation the origination of new varieties is favoured, 

 and that by man's labour many varieties are acquired 

 which, under natural conditions, would be lost ; but nothing 

 justifies the assumption that the tendency to the formation 

 of varieties is so extraordinarily increased that the species 

 speedily lose all stability, and their offspring diverge into 

 an endless series of extremely variable forms. Were the 

 change in the conditions the sole cause of variability we 

 might expect that those cultivated plants which are grown 

 for centuries under almost identical conditions would again 

 attain constancy. That, as is well known, is not the case, 

 since it is precisely under such circumstances that not only 

 the most varied but also the most variable forms are found. 

 It is only the Le^umtnosae, like Pisum, Phaseolus^, Lens, 

 whose organs of fertilisation are protected by the keel, 

 which constitute a noteworthy exception. ' Even here there 

 have arisen numerous varieties during a cultural period of 

 more than 1000 years under most various conditions; these 

 maintain, however, under unchanging environments a sta- 

 bility as great as that of species growing wild. 

 * \Phaseolus nevertheless is insect-fertilised.] 



B. H. 24 



