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 the greater number 

 of novelties, are of hybrid origin. Here we 

 may discern two cases. Hybrids may be 

 produced by the crossing of old types, either 

 of two old cultivated forms or newlv intro- 

 duced 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. If 

 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- 



