76 



found from 50 to 125 white -f grey kernels per kilogram (30,000 kernels) in 

 different parts of the crop of 1906 at Svalof from a stock known as "A." A 

 new stock (C) of this sort was also under cultivation in 1906, and although 

 all white kernels had been removed from the seed sown, the harvest showed 

 from 23 to 29 white kernels in different samples examined. A stock of Black 

 Bell oats which had not been hand picked contained, in 1906 from 35 to 75 

 white kernels per kilogram, while another stock from which all white kernels 

 had been removed for the two preceeding years produced only from 14 to 22 

 white kernels per kilogram. Hand picking of these sorts has been continued 

 by the Seed Company every year since 1906 with the result that only very 

 few white kernels are now found in the commercial sample. In this way the 

 purity of commercial stocks is maintained to such a degree as is possible. 

 That the occurrence of white-grained oats in black-kernelled sorts is often 

 due to spontaneous changes the dropping out or the lapsing into latency of 

 a factor for black, in individuals which normally possess this color has also 

 been pointed out (51, p. 139-156). 



In discussing constancy in the color of the grain of oats attention is 

 drawn to modifications (not hereditary differences) which frequently are 

 found in black, yellow and grey-kernelled sorts. Black oats from the north 

 usually take on a lighter shade when grown in Scania (Skane), the most 

 southern province. This is in no sense an hereditary change, neither is it a 

 degeneration. The alteration in color is simply the result of a change in 

 environment. According to investigations by Atterberg of Kalmar the per- 

 centage of phosphoric acid in the soil has a decided influence on color of 

 grain. Soil rather than climate is in fact generally regarded as the most 

 potent factor in effecting color changes. 



V. PRACTICAL APPLICATION OF PRINCIPLES OF CEREAL 

 BREEDING NOW RECOGNIZED AT SVALOF. 



The work of cereal breeding at Svalof within recent years (since 1901- 

 1902) has come to consist chiefly of special line breeding from the best old 

 varieties and artificial hybridization (46, p. 165-170; 47). By line breeding 

 is meant the taking out of individual mother plants from a mixed popula- 

 tion without special regard as to whether the said plants are botanically or 

 Line- morphologically different or not. This practice is based on the discovery 



m ^' that strains which may resemble each other closely in outward appearance 

 may conceal quite distinct physiological differences. A progressive system 

 of selection cannot therefore be limited simply to visibly different strains. 

 Rather must it be extended to embrace strains which differ in physiological 

 characters as well. In accordance with this idea there is now taken out for 

 separate culture and for a comparison of their progeny a large number of plants 

 irrespective of morphological characters. Thus has the system of exclusive 

 Form breeding or "Form separation" of earlier days been extended to what 

 has come to be 'known as Line Breeding. 



