PEDIGREED NURSERY STOCK l.")7 



SELECTED STRAIN. 



We have seen that the seed sport arises as a sudden variation or 

 mutation from the fixed type. In other cases variations from the type 

 may be developed gradually, as has been done in the cases of many se- 

 lected strains advertised by seedsmen. I have in mind a certain neigh- 

 borhood in which the gardeners are growing a peculiar type of lettuce 

 for which they have no special name. They are engaged in forcing let- 

 tuce and grow their own seed. More than a quarter of a century ago 

 they started with a standard variety. Gradually by rigid selection of 

 parent stock and propagating through all these years only from plants 

 showing some tendency to develop or mutate in a certain desirable di- 

 rection they have produced a strain which is in some ways distinct 

 from the original type and which suits their particular purpose much 

 better. It is evident that this process js in effect one of accumulating 

 or adding together slight mutations all of which tend to develop or 

 progress in a certain direction. Plants of those types which have been 

 developed in this way may properly be called pedigree plants. Numerous 

 other instances of this kind of mutation might be cited had we time to 

 consider them. 



We have seen that under the sexual methods of reproduction new 

 varieties may be obtained either by selecting chance seedlings of a 

 known single parent or by cross breeding from distinct parents. We 

 have seen also that among fixed types new varieties may be developed 

 from suddenly appearing distinct variations called seed sports or muta- 

 tions or they may be produced by gradual processes as in selected 

 strains. 



Let us next inquire whether new varieties may originate by asex- 

 ual propagation. 



Graft Hybrids. — Are new varieties ever produced asexually which 

 correspond to the hybrids produced under tiie sexual method by cross- 

 fertilization? Claims have sometimes been made that it is possible to 

 produce new varieties by grafting which are entitled to be called "graft 

 hybrids." The work which Daniel has done in France demonstrates that 

 this has been done. Other authentic cases are also on record. As a 

 matter of fact, however, it is universally conceded that graft hybrids 

 are exceedingly rare. 



Bud Sports. — Bud sports are weJl known. They correspond to seed 

 sports in that they appear suddenly. Thej- usually show permanently in 

 their new characters when propagated, entitling the sport to be called a 

 new variety or mutation, yet some bud sports prove quite unstable when 

 propagated. 



Numerous instances in which new varieties have originated as bud 

 sports are found among ornamental plants and they are not unknown 

 among orchard fruits. More than one case is known where bud sports 

 have appeared on the Concord Grape. I am perfectly tamiliar with one 

 instance of this kind. From a bud near the base of the main stalk of 



