E. R Saunders 371 



sulphur-white was used as jj" or $. When crossed with glabrous 

 white or glabrous sap-coloured strains F^ was hoary and sap-coloured. 

 If a full sap-colour as e.g. red was used, a full colour was obtained in F^. 

 This type of sulphur-white contains the hoary factor K^, and one of the 

 two factors C and R necessary for the production of sap-colour; the 

 one present must be the one which occurs in Princess May (= R). The 

 other colour factor (C) and the factor which turns red blue (B) are 

 both absent. We can therefore express the composition of this type 

 of sulphur-white thus — hcRK. The seed obtained from Herr Benary 

 showed the characteristics described under type 1 (p. 867, seeds small, 

 brown, irregular). This form evidently has the coi^position bCrK, and 

 has also a factor causing paleness, so that in a cross a full sap-colour 

 carried by the other parent becomes pale in Fi. This type when bred 

 with glabrous cream or a glabrous sap-coloured form gives F^ all 

 hoary sap-coloured ; with glabrous white on the other hand it gives 

 Fi all glabrous white. Bred together these two sulphur-whites should 

 give a sap-coloured hoary F^ of a pale red colour (=rose). It was 

 hoped that plants from this mating would have been raised this year, 

 but unfortunately owing to the bad season in 1910 no good seed was 

 obtained. Indirect proof however is already forthcoming, for a mating 

 in the form 



[sulphur-white (type 2) x glabrous red] x sulphur-white (type 1) 

 gave all rose hoary (217); whereas the mating 



[sulphur-white (type 2) x glabrous red] x sulphur-white (type 2) 



gave the expected result — half the offspring being red hoary and half 

 white smooth. 



The expense incurred in the course of the present work has been in 

 part defrayed by a grant from the British Association for the Advance- 

 ment of Learning, and also during the present year by a grant from the 

 Gordon Wigan Fund. The experiments were carried out in one of the 

 allotment gardens of the Cambridge Botanic Garden, which for some 

 years, by the kindness of the Botanic Garden Syndicate, has been 

 permitted rent free. 



I wish here to express my thanks to Miss Killby, who in the course 

 of the work has given me much valuable assistance in the garden, and 

 who kindly took the photographs here reproduced ; also to those friends 

 who were kind enough to raise and record a number of the plants. 

 1 See Evolution Report IV. p. 36. 



