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 X 
a EN ya ce rd whe oon 
Types oF MatiInG IN Fy 
F2 indi- Number F2 indi- Number F» indi- Number F?2 indi- Number 
viduals of viduals of viduals of viduals of 
mated mating mated mating mated | mating mated mating 
AXX 10 BXZ' 46 COEOr: 51 EXE 19 
AXY 12 BXB 13 CxXiG 5: EXF 45 
AXZ 40 | BXe Eye el vice al, ode 1ea cere: 47 
AxXZ’ 42 BX D 29 DXY 24 FFXX 30 
AXA 11 BXE 55 DXZ 52 FXY 32 
AXB 33 BXF 57 DxaZ 54 FXxXaZ 60 
AG, 25 BxX@G 59 DX D lif, FXaZ’ 62 
AxXxD 35 CGE 18 DXE 43 FXF 21 
AXE 61 Coxe 20 DXF 31 FXG 49 
AXF 63 CXZ 48 DxX@ 27 GX xX 34 
AXG 65 Cx az! 50 EXX 26 GX Y 36 
Bxx 14 C256 GC 15 HXY 28 GXZ 64 
BX Y 16 Cx D 39 EXZ 56 Gx Z’ 66 
BXZ 44 CXE 41 EXZ 58 Gx@ 23 
Fig. 172, Table LVI.—Illustrating a system of labelling Fi and F2individuals resulting 
from any type of mating. (Adapted from Pearl.) 
Order of precedence: female named first in every cross; X 2 K Yo! = mating (1); 
YQ XX =mating (1);in back-crosses later generation 2 X earlier generation o ranks 
first, thus Z9 X Xo = mating (2),X2@ X Zo = mating (2’), etc. 
Digitized by Microsoft® 
