INHERITANCE— IMPRO VEMENT B 1 ' BREEDING 2 o 9 



may involve us in complications difficult to unravel. With CHAP, 

 our present knowledge of genetics, the safest course to follow V ' 

 is to work step by step, building up the new type, one character 

 at a time, rather than to attempt to add two or three characters 

 at once. 



Promiscuous or aimless crossing, and crossing which is 

 not followed by rigorous selection, is worse than useless, for 

 it spoils an established breed only to produce a mongrel race. 

 Vacillation in breeding is equally unproductive; success is 

 then mere chance, and we work like men lost on the veld, 

 wandering sometimes forwards, sometimes back on our tracks. 



In order to breed intelligently and to good purpose, it is 

 necessary not only to know what we want, but also how to 

 attain it, which involves a close and thorough study of each 

 breed. In the case of maize, our ideal should include not only 

 the colour and shape of the grain and ear, but also the average 

 yield of grain from each ear, and the average stand of plants 

 per acre. 



Briefly, we may say that there are three things essential 

 to the development of pedigree stock, whether of animals or 

 plants : (1) start with the best stock you can get ; (2) propa- 

 gate only the best (which implies also the elimination of the 

 unfit) ; (3) improve by crossing, when you know how to ob- 

 tain and fix the desired character. 



164. Methods of Plant Breeding. — The methods employed 

 in the breeding of plants are much the same as those used 

 with domestic animals — horses, cattle, sheep, pigs, or poultry. 

 The fundamental point, after the determination of the desired 

 type, is the continuous mating (i.e. without interruption) of 

 those parents, both male and female, which most nearly 

 approach that type. 



In the breeding of plants three principal courses are 

 followed: (1) selection, (2) cross-fertilization, and (3) hybridi- 

 zation. Inbreeding necessarily follows any one of these three 

 methods. 



Selection may be roughly defined as the choice of suitable 

 parents for the production of a strain of the desired type. 

 They may belong to the same or to different breeds. Selec- 

 tion implies that there is a choice of characters to select from. 



It is necessary to resort to selection and inbreeding to 



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