298 



GENETICS IN RELATION TO AGRICULTURE 



has accomplished so much. His methods of hybridization, also, have 

 been such as to economize time rather than insure certainty as to ancestry. 



Nigra 

 Americana 



Alhambra 



c. 



Triflora 

 Simoni 



French Prune 



Pissardi 



a 



Kelsey 



fio. 119. Ancestry of the Alhambra plum. 



His aim has always been the tangible result rather than advancement of 

 scientific knowledge. 



Clonal Selection. Under the term clonal selection is included all 

 methods of plant improvement based upon the utilization of asexual 

 means of multiplication, whether by selecting the most favorable clones 

 from a mixed population, or by selecting and propagating favorable varia- 

 tions within clones. In potatoes many commercial varieties are definitely 

 known to be mixtures of different clones, and improvement may be 

 effected by simply selecting those which are most productive and most 

 desirable fro'm a market standpoint. A unique instance of clonal 

 selection is that followed in Oklahoma and other regions along the north- 

 ern limits of the range of Bermuda grass. There the cold winters kill 

 off the less hardy strains; those that remain are propagated by distribu- 

 ting sod. In alfalfa many improved strains have been produced by 

 the selection and multiplication of superior individuals. This work has 

 been carried on by the Bureau of Plant Industry of the U. S. Department 

 of Agriculture and various stations, especially those in South Dakota, 

 Kansas and Arizona. The propagation of improved strains by means 

 of cuttings is of great practical value, and Hansen recommends the use 

 of tobacco planting machines for the setting of rooted alfalfa cuttings. 



A phase of clonal selection which has recently come into prominence 

 is bud selection, although the occurrence of bud variations, particularly 

 of bud sports, has long been a matter of common knowledge. Munson 

 (1906) seems to have been the first to call attention definitely to the pos- 

 sibilities in fruit improvement by selection of buds from superior indi- 

 viduals or vegetative parts, although Bailey had on several occasions 

 previously pointed out that varieties sometimes originated from buds. 

 During the past ten years many practical experiments in bud selection 

 have been conducted, but with diverse results. 



