608 Mutations 



nated in horticulture as varieties, though ob- 

 viously they are of quite another nature than 

 the varieties reproduced by seed Secondly, a 

 large number, no doubt even the very largest 

 number of the novelties, are of hybrid origin. 

 Here, too, we may discern two cases. Hybrids 

 may be produced by the crossing of old types. 

 either of two old cultivated forms or newly 

 introduced species, or ordinarily between an old 

 and an introduced variety. Such novelties are 

 excluded from our present discussion. Sec- 

 ondly, hybrids may be produced between a true 

 new mutation and some of the already existing 

 varieties of the same species. Examples of this 

 obvious and usual practice will be given further 

 on, but it must be pointed out now that by such 

 crosses a single mutation may produce as many 

 novelties as there are available varieties of the 

 same species. 



Summarizing these introductory remarks we 

 must lay stress on the fact that only a small part 

 of the horticultural novelties are real mutations, 

 although they do occur from time to time. It 

 useful they are as a rule isolated and multiplied, 

 and if necessary, improved by selection. They 

 are in many instances, as constant from seed as 

 the unavoidable influence of vicinism allows 

 them to be. Exact observations on the origin, 

 or on the degree of constancy, are usually lack 



