Inheritance of Hoariness in Stocks (Matthiola). 541 



it follows that strains which lack C or K or both will be glabrous even though 

 the factors H and K are both present. 



On these assumptions the statistical results which were obtained from 

 various unions between glabrous sap-coloured and non-sap-coloured forms 

 could be accounted for, and the composition of the several types employed 

 represented in terms of these factors as follows : — 



Glabrous cream cEHK. 



Glabrous white CrHK. 



Various glabrous sap-colours CEHk. 



It has since been pointed out by Doncaster that the supposition that two 

 factors are required to produce hoariness in a zygote containing C, E introduces 

 an unnecessary complexity ; for if, as appears to be the case, the manifestation 

 of hoariness in these strains is conditioned by the presence of the two sap- 

 colour factors (C and E), then the existence of one additional factor is all that 

 is required to account for the several results given above (see 1, 2, and 3). The 

 justice of this criticism was acknowledged, and in the later accounts of these 

 experiments Doncaster's simplification has been adopted, and the unnecessary 

 factor (H) omitted from the formulae of the several types. More recently, 

 however, I have employed another sap-coloured form, and the results obtained 

 with this new type make it clear that the earlier hypothesis that hoariness is 

 determined by two factors, though not justified by the facts at the time it was 

 put forward, is in fact correct, and consequently that the original scheme may 

 be held to stand. This new type is a glabrous sap-colour known commercially 

 as .marine blue. Crossed with the original glabrous sap-colours, e.g. azure, 

 flesh, and red, it gives all hoary in Fi, whereas these latter types, as stated 

 above, give all glabrous when crossed together. On the other hand, when 

 mated with glabrous whites from some new strains which had given, as before, 

 all hoary with the original sap-colours, it gave an Fi all glabrous. In short, 

 marine blue gave results exactly the reverse of those previously obtained 

 with other sap-colours. Eeciprocal unions were carried out in both cases. 

 We must, therefore, conclude that the marine blue strain lacked the factor K 

 which is present in the other sap-coloured forms employed, but contained 

 another factor not present in these other forms, a factor complementary to K 

 in the same way that C is to E, the factor H referred to above, in fact, the 

 postulation of which had not been warranted by the earlier results. The fact 

 that two factors in addition to the colour factors C and E are required to 

 produce hoariness being thus established, we can retain in their entirety 

 the diagrams appearing on pp. 40 and 41 of Eeport III* representing the 

 * See footnote, p. 540. 



