390 



GENETICS IN RELATION TO AGRICULTURE 



in a new generation, they were made from the plants most typical and constant 

 for the pattern concerned. When a bud variation appeared, if the conditions 

 were favorable, the parts possessing it were allowed to develop until there were 

 several branches from which cuttings could be taken simultaneously. In such 

 cases the selection of branches for the new type was a simple matter, as it 

 depended on the taking of branches sharply distinct from the main part of 

 the plant. . . . When further cuttings were made for a new generation to 

 perpetuate the type they were made from plants most uniform and constant 

 (determined from the records) for the pattern in question. Usually but three 

 cuttings were taken from a plant and these were taken from branches most uni- 

 form and clearly conforming to the type." 



The relative numbers of "constant" plants and of plants showing 

 either clear-cut bud mutations or "fluctuations" are of considerable 

 interest in connection with this matter of maintaining strains. These 

 proportions are given in the tabulated summary of the main clones that 

 were derived from one of the two original plants Table LV. Clones 11 



TABLE LV. GENERAL SUMMARY OF CLONES DERIVED FROM PLANT No. 1 



and 12 were derived from two branches that had the same color pattern, 

 yet it seems that they possessed "quite different potentialities for con- 

 stancy and for bud variations. Even more marked differences than these 

 developed among the various subclones. A study of pedigrees shows that 

 in all patterns and in all main clones there were certain lines of progeny 

 much more constant than many others. These could not be detected by 

 any other than a pedigree method." These facts have a definite bearing 

 on the maintenance of vegetatively propagated varieties or strains. If 

 similar diversity as regards degree of variability exists in other cultivated 

 plants, as it undoubtedly does, careful bud selection must be of prime 

 importance in keeping varieties true to type or at least in preventing 

 deterioration through the accumulation of undesirable bud mutations. 

 In Coleus at least it is certain that bud selection is effective and necessary 

 in maintaining strains true to type. If it is equally potent in its effect 

 on other vegetatively propagated plants, bud selection should be given 

 far more attention by nurserymen than it has generally received. 



