variations: how induced 315 



The most certain method of inducing variation in a plant is 

 to cross or hybridise it with another individual. In this process, 

 there is a mixing of the protoplasm of two distinct plants, and 

 the offspring therefore consists of living matter derived from two 

 distinct and unlike sources. Sometimes the plants of the first 

 and second generation obtained from such a cross all resemble 

 each other very closely. Succeeding generations, however, exhibit 

 very great variability, the plants showing the characters of the two 

 original parents blended in very variable degree, and peculiar- 

 ities not seen in the parents are very frequently observed among 

 them. The latter characters although apparently new are often 

 those possessed by the grandparents or earlier ancestors of the 

 plant which have been transmitted in a latent state through 

 several generations. 



Variations which appear as the result of crossing are much 

 more frequently hereditary than characters produced by the 

 action of external conditions ; moreover, they can generally 

 be increased by selection. Not only is crossing of use for the 

 purpose of inducing variability among plants so that selection 

 may be begun ; it is sometimes resorted to in order to combine 

 in one variety of plant characters previously possessed only by 

 two different and separate varieties. A tender variety which is 

 of good quality in other respects when crossed with a hardy 

 kind of poorer quality, sometimes gives rise to one or more 

 descendants, combining the good quality of the former with the 

 hardiness of the latter : similarly other qualities of two distinct 

 varieties may be blended more or less satisfactorily, although 

 in most cases much selection is needed to fix and augment the 

 peculiarities of the new type thus obtained. The combination 

 of certain peculiarities cannot be attained in one and the same 

 plant by any means ; it is often better to grow one variety for 

 one purpose and another for another purpose, rather than 

 attempt the combination of antagonistic features (see next 

 paragraph). 



