408 THE WHEAT PLANT 



Mass Selection. The selection of a number of the best ears from an 

 ordinary crop of wheat, and the grading of the grain by sieves and other 

 machines in order to obtain the largest for use as seed, has been practised 

 by the most advanced agriculturists in all ages. Virgil (Georgics, i. 197) 

 says : 



" I've seen the largest seed, tho' viewed with care, 

 Degenerate, unless the industrious hand 

 Did yearly cull the largest." 



Columella (De re rustica, ii. 10) also refers to the necessity for 

 sifting out the largest grains for use as seed, and mentions that Celsus 

 advises, where the crop is small, to pick out all the best ears and store 

 them for seed ; Varro (De re rustica, i. 52) similarly advises the 

 selection of the best ears for seed. 



The process of mass selection, as generally practised, consists in 

 choosing from the standing crop 100, 1000, or some other arbitrary 

 number of ears possessing characters which the plant-breeder considers 

 it desirable to fix or increase. The choice may be based upon the excep- 

 tional length or density of the ear, the number of grains in the spikelets, 

 the height of the straw, or other characters. The grains from these 

 selected ears are sown, and from their progeny a further selection is made, 

 and the process repeated annually as long as it is deemed desirable. 



When carried out by skilled observers acquainted with the morpho- 

 logical differences of wheat plants, mass selection rapidly leads to the 

 establishment of a uniform type of plant from a variable crop, and appar- 

 ently new or improved forms have been frequently obtained by this 

 means in various countries. When the characters upon which the selec- 

 tion is based are correlated with prolificacy of the plants, it results in the 

 production of a crop whose yielding capacity gradually increases from 

 year to year as the selection is continued. 



Where improvement occurs, it is the custom to assume that the crop 

 is, in the first instance, a mixture of a number of distinct and independent 

 forms and the selection does nothing more than isolate one of these from 

 the rest, just as a white-chaffed form would be established by selecting all 

 the ears with white chaff from a field mixture of white- and red-chaffed 

 wheats. 



Whatever the explanation, the fact remains that mass selection has 

 led to an improvement in the yield and uniformity of the crop when 

 applied to fields of wheat as ordinarily cultivated on the farm, and it is 

 a method which should not be abandoned nor despised. 



Apart from the possibility of obtaining new forms by its means, the 

 process is invaluable in maintaining the purity of those wheats which have 

 descended from single ears. 



Individual Selection. The selection of single ears or plants and their 



