PLANT-BREEDING METHODS 



423 



A system of labeling and recording that will be at once concise and 

 definitely descriptive of the individuals and the nature of the matings 

 has obvious advantages. Pearl has devised a system which is especially 

 useful in crossbreeding experiments and in work with self-sterile plants; it 

 can be adapted for any material. By the use of letters to denote indi- 

 viduals or types of individuals that are brothers and sisters and numbers 

 to denote types of matings a perfectly general set of terms is provided 



P, 



F, 



F, 



TYPES OF MATING IN 



FIG. 172, Table LVI. Illustrating a system of labelling Fi and Ft individuals resulting 

 from any type of mating. (Adapted from Pearl.) 



Order of precedence: female named first in every cross; .X" 9 X Y(? = mating (1); 

 F 9 X Xd 1 = mating (10 ; in back-crosses later generation 9 X earlier generation cf ranks 

 first, thus Z 9 X X<? = mating (2), 3" 9 X Zo" = mating (20, etc. 



