316 GENETICS IN RELATION TO AGRICULTURE 



form retained the other distinctive characters of its parent. Finally, 

 as Boshnakian points out, similar sports have been secured among sexually 

 produced progeny in other species of Nephrolepis. Thus it appears 

 that these interesting and valuable ornamentals owe'their origin to altera- 

 tions in specific genetic factors, i.e., to factor mutations in vegetative 

 reproduction. 



We have found that new varieties of cultivated plants may be arti- 

 ficially produced in either of two ways, viz., by the discovery and pre- 

 servation of mutations or by hybridization. Factor mutations occur in 

 both sexually and asexually reproduced plants and frequently produce 

 new forms of immediate economic value. Sometimes, however, the 

 original mutation may be merely a starting point indicating the line 

 along which selection must work. There is always the possibility that 

 subsequent mutations in the same direction, even though they be 

 minute, will be taken advantage of by the breeder. In the creation of 

 new varieties for special purposes hybridization must usually be employed. 

 The success of breeders in combining the desirable qualities of several 

 species in the best modern varieties of the rose suggests untold possi- 

 bilities in this field of plant breeding. 



