PEACTICAL APPLICATIONS 205 



or, in other words, of forms which will hand on their desirable 

 qualities to future generations by heredity. This does not matter 

 in the case of fruit trees and other plants which can be propa- 

 gated by buds independently of sexual reproduction. As a 

 general rule, a fruit tree cannot be relied upon to come true 

 from seed, the characters which it has received from different 

 ancestors not being permanently combined, but separating out 

 and undergoing fresh combinations in the sexual process, pro- 

 bably in accordance with Mendelian principles. The seedlings 

 will therefore be " degenerate," as horticulturists say, and will no 

 longer exhibit those valuable qualities which depend upon the 

 confluence in one individual of particular lines of ancestry. 



The majority of Burbank's productions could not survive in a 

 state of nature at all ; they are essentially artificial and have to 

 be artificially propagated by means of buds or cuttings. In this 

 respect they are quite different from the pure races which it is 

 possible to produce by hybridization carried out in accordance 

 with Mendelian principles, in which new and permanent com- 

 binations of unit characters, capable of being transmitted by 

 heredity, are effected. 



Professor Bateson, Professor Biffen, Mr. Hurst and others have 

 lately done much to demonstrate the possibilities of progress in 

 this direction, and the value which the application of the 

 Mendelian principles of heredity must have from the economic 

 point of view. We know now that such cereals as wheat and barley 

 obey the Mendelian laws of hybridization as regards various 

 important characters. So also do horses as regards the colour of 

 their coats, and human beings as regards the colour of their eyes, 

 and in some other respects, especially as regards the inheritance 

 of certain diseases. In short, it appears certain that Mendelian 

 principles have a very general application, and the economic 

 value of the knowledge of such principles must be enormous. 

 Professor Biffen has shown, for example, that susceptibility and 

 insusceptibility to that destructive disease in wheat known as 

 " rust," behave as Mendelian characters, and that it is possible 

 by a very simple process of hybridization to confer immunity 

 from this disease upon naturally susceptible varieties. 



From the theoretical point of view the great value of the 

 Mendelian experiments lies in the possibilities which they present, 

 at any rate in certain cases, of analyzing the constitution of the 

 hereditary substance (germ plasm), and thereby gaining some 



