G. P. HECTOR 169 
Here A is due to two interacting factors, B to three, vz., the two respon- 
sible for A together with an additional one, all three being necessary for the 
production of colour in B. Thus— 
36 A : 28 a 
A +} 
ABC :,ABe = AbC =; aBC. : Abc 3 aBe = ab@. 3 ab 
DAT RED) ene 3 9 a vs : 3 5 og J il 
Re} 
20 By: 37 b 
or “ie 27 AB : 9 Ab: O aB: 28 ab 
Observed .. 1,972 : 699 : 0 : 1,998(4,669 plants, 7 families) 
Expect ae, 1,969°29- =: 656-43 2 0 : 2,042-25 
SuMMARY. = 
1. These colour characters which we have been discussing are sometimes 
simple, due to single factors or to several interacting factors. But frequently 
they are grouped into patterns or systems (e.g., “leaf-sheath, apiculus, 
stigma ”’), which are inherited as a whole and segregate as if due to a single 
unit factor or to the same interacting factors. There is evidence, however, 
that the constituent parts of these patterns may be due to different factors, 
in which case they must be completely linked. The evidence consists, first, in 
the fact that rare instances are found where the patterns break down. Four 
such cases have been found : (1).In the cross Noachur <x Pookhi, the pattern 
‘coloured internode and stigma ”’ was found to break down three times out 
of 1,199 plants examined, giving 3 types in F, with “coloured stigma and 
green internode’. (2) In the same cross the pattern “ coloured leaf-sheath 
and apiculus ” broke down twice out of 1,199 plants, giving two types in F, 
with ‘‘ coloured apiculus and green leaf-sheath.” (3) In the cross Bailabakei 
x Pookhi, the pattern “ coloured leaf-sheath, internode and stigma ” broke 
down 24 times out of 4,687 plants examined, giving 24 plants with coloured 
leaf-sheath and stigma but green internode. (4) In the cross Agartollah x C25 
the pattern “coloured leaf-sheath, pulvinus, auricles, internode, glumes, 
apiculus ’ broke down once out of 4,669 plants examined, wz., one plant was 
found with colour in the glumes and apiculus, but with green leat-sheath, 
internode, pulvinus and auricles. 
These exceptional cases might be simply mistakes in observation, but all 
were Very carefully examined and if colour was present, it must have been 
developed to so small a degree that it could not be observed by the most 
critical examination, whereas the type plants had the colour strongly deve- 
loped. It is to be noted, moreover, that all are cases in which colour failed 
2 
