540 



Further Contribution to the Study of the Inheritance of Hoariness 

 in Stocks (Matthiola). 

 By Edith E. Saunders, Lecturer and late Fellow, Newnham College, 

 Cambridge. 



(Communicated by W. Bateson, F.R.S. Received August 1, 1912.) 



In an earlier account, in which the results of intercrossing various strains 

 of glabrous ( = wallflower- leaved) Ten-week stocks are described, it has been 

 shown that the results are capable of explanation on the supposition that 

 a certain inter-relation exists between the factors causing hoariness and 

 those concerned in the production of coloured sap.* We may briefly recall 

 the main facts in regard to these two characters. It was found experi- 

 mentally — 



(1) That glabrous sap-coloured strains of various colours (e.g. dark purple, 

 light purple, azure, red, flesh, copper) when intercrossed, produced offspring 

 which were also all glabrous sap- coloured ; later generations derived from 

 these crossbreds were again invariably of this type. 



(2) That these same glabrous sap-coloured strains, when crossed with the 

 glabrous non-sap-coloured forms white or cream, gave all sap-coloured hoary 

 in Fi ; further, that self- or inter-bred Fi plants gave an F 2 composed of the 

 three classes, sap-coloured hoary, sap-coloured glabrous, and non-sap-coloured 

 glabrous, in the proportion approximately of 9:3:4. There were no non- 

 sap-coloured hoary. 



(3) That unions between the two glabrous non-sap-coloured forms white 

 and cream also gave F 2 all sap-coloured hoary ; in F 2 the proportion of forms 

 was about 9 sap-coloured hoary to 7 non-sap-coloured glabrous. In this 

 case sap-coloured glabrous were absent, as well as non-sap-coloured hoary. 



The suggestions put forward at the time in explanation of the above facts 

 were — 



(a) That two factors (C and R) must be assumed to be present in all 

 sap-coloured forms ; in the absence of either or both the sap is colourless. 



(b) That hoariness similarly is due to the presence of two factors (H and 

 K), but that this second pair becomes ineffective under certain conditions 

 (see (c)). 



(c) That an inter-relation must exist between these two pairs of factors of 

 such a nature that the hoary condition due to the presence of the H, K pair 

 only becomes manifest in a zygote which also contains the C, R pair. Hence 



* ' Reports to the Evolution Committee of the Royal Society,' Report III, p. 38. For 

 details of the experiments, see Reports I and II. 



