G. f. HECTOft 9b 



If this explanation is correct, then the constitution of the Fi plants 

 with reference to the stigma must be Cc Rr Pp and these on selfing will give 

 rise to : — ■ 



(1) 27 plants of constitution CRP— coloured stigma, red leaf-sheath, red apiculus. 

 „ CR — white ,, ,, 



» P^ — '■ .> green leaf-sheath and apiculus. 



CP— „ 



C— „ 

 P— 



„ crp — ,, ,, ,, 



i.e., 27 coloured : 37 white stigmas or 1:1-3. 



The interesting point in these cases lies in the fact that the 9 plants of 

 constitution CR would normally be expected to have stigmas of a reddish 

 colour like the leaf-sheaths, as both the factors necessary for the production 

 of red colour in the leaf-sheath and apiculus are present here in the stigma, 

 the purple factor P only being absent, but in not a single case could a trace 

 of colour be found in these. What the explanation of this is has not yet been 

 determined. A possible explanation is that there is here some factor in the 

 stigma which inhibits the production of the colour, except when the additional 

 factor P is present. If so, then these white stigmas of the constitution CR 

 should prove dominant over similarly constituted red stigmas amongst coloured 

 types. Amongst the coloured stigmas, it was possible to detect various shades, 

 some apparently red, but no attempt has yet been made to separate these. 

 This also would explain the occasional occurrence of pure-breeding types 

 with coloured leaf-she iths, apiculus and white stigma, the second class referred 

 to in the beginning. Such types may have been produced through the agency 

 of natural crossing and some may prove to be dominant whites. If so, then 

 these cases would seem to be comparable to the red-stemmed, dominant 

 white flowers described by Gregory^ in the case of Primulas. 



Assuming this explanation, in the F3 generation out of every 27 coloured 

 stigmas, 



1 should produce coloured only. 



6 „ „ 3 coloured : 1 white. 



12 „ „ 9 coloured : 7 white. 



8 „ „ 27 coloured : 37 white, 



and it should also be possible to produce the colour by inter-crossing many 

 of the whibes. 



' Gregory, loc, cit., p. 115, 



