168 Inheritance in the Stock (Matthiola incana) 



quarter-hoary grades, is a heterozygote containing, like all the partially 

 hoary grades, the 4-factor group GRH^K, but having only a single dose 

 of both H^ and K. The slight degree of hairiness manifested is con- 

 ditioned, as in the partially hoary grades containing a double dose of one 

 or both of these determiners, by the presence of the colour couple. (For 

 these reasons a certain advantage would no doubt have been gained by 

 drawing the arbitrary line between the partially hoary and sub-glabrous 

 categories so as to include this case in the former instead of the latter 

 class, only at the cost however of some absurdity in practice in applying 

 this terminology to a plant so nearly glabrous.) 



13. The lower grade in the same linear series [(6)] shows the slight 

 effect, only barely perceptible (1 — 2 solitary hairs on the basal margins 

 of a few leaves), produced by K either with or without the colour couple, 

 and independently of H and H^. 



14. The two grades [(c) and (c?)] comprised in the other sub-glabrous 

 group exhibit a distribution of hairs characteristic of H and H^ only 

 when present in conjunction with GR. In this respect therefore both 

 allelomorphs differ from the complementary factor K. 



1.5. All individuals not included in the preceding categories, that 

 is to say all whose factorial constitutions lack K, and also the combina- 

 tion of H or Hi with GR, appear to be entirely destitute of hairs. They 

 stand at the zero end of the scale and together form the wholly glabrous 

 group. 



16. It follows from (13) and (14) that hair production can occur to 

 some slight degree when only one of the two complementary factors for 

 hoariness [H (or H^ and K'\ is present. 



17. The broad effects resulting from the interaction of the com- 

 plementary factors for surface character [H (or H^ and K'\ with the 

 colour couple {GR) can be stated in general terms thus : 



Factorial Combinations Effect as regards Hair Production 



(1) H (or ffi) without GR Nil 



(2) K with or without CR Minimal, localised in a particular region 



(3) Hi with CR Minimal, localised in different regions 



(4) H with GR Relatively slight but considerably more ex- 



tensive than in (2) and (3), localised 

 in several distinct regions 



(5) One dose of HiK with GR Somewhat similar in magnitude to (4) but 



localised in different regions 



(6) As (5) but with the addition of a second Successively increasing, but still unequally 



dose of K or Hi or both distributed in different regions 



(7) HK in any dose with GR Maximal, overspreading all regions to the 



fullest extent 



