154 Inheritance in the Stock (Mattliiola incana) 



Summary of Earlier Results. . 



1. The fully hoary condition is dominant to glabrousness. 



2. Full hoariness is primarily dependent upon the presence of a 

 pair of factors denoted by H and K. 



3. The HK couple is only fully effective in those individuals which 

 contain in addition another pair of factors, G and R, upon the presence 

 of which the appearance of anthocyanin in the petals depends. In other 

 words the GR couple may be looked upon as constituting a limiting 

 factor conditioning the manifestation of the HK effect (full hoariness). 



4. All four factors segregate separately, hence every factorial combi- 

 nation can be obtained by suitable matingS. 



5. Individuals containing all four factors, whether homozygous or 

 heterozygous in respect of any or all, are fully hoary, in other words 

 only one dose of each factor is required to produce full hoariness. 



6. Partial hoariness results, when H is replaced in the GRHK 

 group by another factor indicated in the earlier accounts hy J. 



7. An individual homozygous for all the four factors GRJK exhibits 

 the condition described as half-hoary. [That only one dose oi»CR is 

 however essential, both here and in the following case, will appear later.] 



8. If the half-hoary form is crossed with a glabrous individual of 

 the composition GRK the resulting heterozygote is of the lower inter- 

 mediate grade termed quarter-hoary. 



The above inter-relations having been established there remained 

 to be investigated the appearance and behaviour of individuals con- 

 taining the various other possible combinations of C, R, H and K 

 with /. The further study which this work has entailed has not only 

 resulted in an addition of new forms to our list of biotypes, but has 

 enabled us to carry our factorial analysis to a further point than had 

 hitherto been achieved by inspection alone. Identification by this 

 means is in some cases however decidedly laborious, necessitating close 

 and repeated examination at different stages of development. 



Description of Biotypes. 



In the first place we may draw attention to certain anatomical 

 features common to all grades. A noticeable thickening of tissue occurs 

 in every case at the extremity of the leaf over the termination of 

 the midrib. This region shows the structure of a typical watergland 



