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. : Triflora 
Simoni 
French Prune 
| Pissardi 
| Kelsey 
jFic. 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 from 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. 8S. 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. 
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