130 



The Journal of Heredity 



"By a comprehensive series of trials, 

 the {principle was firmly established that 

 the proijer unit of selection is the sinj^'le 

 ear or head. Further investij^^ation 

 brought out the fact that in an ordinar\' 

 field of oats, wheat, or barley there were 

 dozens of different types, most of which 

 bred true. The next step was to 

 discover the superior types, or those 

 specially adapted for sjjccial conditions. 

 It has been demonstrated that certain 

 characters of apparently negligible im- 

 portance are actually trustworth\- indi- 

 cators of the jDroductive power of an 

 individual and of its quality. This 

 ])rinciple of correlation or association of 

 characters has been found ai:)plicable 

 to all farm crops, and while it sheds a 

 brilliant light to guide the improvement 

 of crojjs, and provides a short ciit to 

 success, it effectively bars any but the 

 trained specialist from the speedy 

 recognition of new varieties by selec- 

 tion." 



There arc two general methods of 

 selection adopted by plant-breeders — 

 7uass selection and individual selection. 



Mass selection consists of the con- 

 tinuous and repeated selection of a 

 number of the best grains, ears, or 

 plants. It is based on Darwin's con- 

 ception of the origin of species, and it is 

 supposed that by the repeated selection 

 of a number of elite ]3lants each year, 

 the race, as a whole, will be gradually 

 im]jroved. 



I3e Vries denies that any jjennanent 

 imi)ro\'cment can result from mass 

 selection. 



Fruwirth, on the other hantl, affirms 

 that mass selection does result in 

 permanent improvement. 



The effect of mass selection, as 

 applied to oats, barley, and potatoes, 

 has been strikingh' demonstrated by 

 Professor Zavitz at Ontario.'^ The 

 following table summarizes the results 

 of sixteen years' continuous mass selec- 

 tion on these crops: — 



AVICRAC.E YIELD IN FOUR YE.\R PERIODS IN BUSHELS PER .ACRE OF 0.\TS, B.\RLEY, .\ND POT.VTOES, 

 SHOWINC; THE EFFECT OF M.\SS SELECTION ON SELF-FERTILIZED AND ON VEGETATIVEI.Y PRO- 

 DUCED CROP-: — 



Mass selection is most effecti\-e when 

 the individual ])lant is made the tmit of 

 selection, and not the individual ear or 

 the individual grain, for it frequently 

 happens that large grains and large 

 cars of wheat are found (jn relatively 

 poor plants. 



Mass selection thus j^ractised lends 

 towards improvement of the type by 

 pro])agating from the best plants and 

 excluding all the rest. It may, of 

 course, hapi)en that some of the selec- 

 tions thus made are sujjcrior because 

 they have been grown under favorable 

 environment. They may, for exami)le, 

 have received an extra amount of sti])er- 

 phosphatc through the irregular working 



'^ Rei)ort, Ontarif) Agricultural College, 190.S. 



of the drill, or they may have l)ecn 

 fax'ored with inore s]jace to develop 

 than the majority of plants in the croj). 

 However, the repeated and rigorous 

 selection of the best plants would 

 gradually confine the choice to what 

 might be tenned the pennanently 

 sujjcrior jjlants, and the general char- 

 acter of the ero]) would gradually im- 

 prove in the desired direction. 



Mass selection has been ]3racticed 

 with great success at the Gennan cxi)eri- 

 ment stations, and b>' such breeders as 

 Rimpau, Drechsler, and Mokry. There 

 are sex'cral different wa\-s in which this 

 method of selection may be ai)])lied. 

 Whatever method is adopted must 



