78 THE PRINCIPLES OF HEREDITY 



and in each new seminal generation the process is repeated. 

 Moreover, as plants produce many more offspring than 

 mammals or birds, the gardener's area of choice in each 

 seminal generation is much wider than the breeder's. Such 

 plants, therefore, have been evolved by a tremendously severe 

 process of selection, resulting in an evolution much more 

 rapid than is possible among the higher animals, or even 

 annual plants. 



135. Now suppose we chose any one of these highly 

 divergent varieties, and, without any selection, bred from seed 

 alone, what again would happen ? There is ample evidence 

 that in the vast majority of instances the variety would 

 swiftly (that is, in a few generations) revert to something 

 very like the wild stock from which it originally descended, 

 but not to the wild stock precisely ; for while the cultivated 

 variety was undergoing progressive evolution in one direc- 

 tion, it was apt under the changed conditions of selection to 

 undergo regression in other particulars, and in these the 

 reverted varieties would differ from the wild stock. 



136. Here, again, the rapidity and completeness of the 

 reversion is proportionate to the rapidity of the previous 

 evolution. It is greater in the case of many cultivated plants 

 than in the case of any domesticated animals. It is greatest 

 in the case of plants most recently cultivated and stringently 

 selected. The peach, which has been cultivated for more 

 than 2000 years, generally comes true by seed. 1 Apples have 

 also been cultivated from antiquity, but there are a great 

 number of recent varieties which, like all recent varieties, 

 are especially liable to reversion. " No one can raise, for 

 instance, from the seed of the Ribstone Pippin, a tree of the 

 same kind. . . . Yet it was a mistake to suppose that with 

 most varieties the characters are not to a certain extent 

 inherited. In two lots of seedlings raised from two well- 

 marked kinds, many worthless crab-like seedlings will appear, 

 but it is now known that the two lots not only usually differ 

 from each other, but resemble to a certain extent their 

 parents." 2 "In a treatise published in Amsterdam in 1768 

 it was stated that nearly 2000 varieties of hyacinth were 

 known. A century later only 700 varieties could be found in 

 the largest garden in Haarlem. In this treatise it was said 

 not an instance is known of any one variety producing itself 

 truly by seed ; the white kinds, however, now almost always 

 yield white hyacinths, the yellow kinds also come true." 8 



1 Animals and Plants, vol. i., p. 361. 

 a Op. cit., p. 372. 8 Op. cit., p. 395. 



