K. S. Salmon 299 



Before we consider the significance of the data collected in Table I, 

 we must note the behaviour towards the mildew of other seedlings of 

 the same parentage and age. First, as regards the susceptibility shown 

 in the hop-garden. In several cases we are able to compare the behaviour 

 of seedlings growing by the side of. and close to, the '"immune" seedlings 

 of Table I: here the factors connected with soil, manuring, climatic 

 conditions and exposure to infection by spores of the mildew are the 

 same, so that any difference in susceptibility that is shown must be 

 attributed to the different ''constitutional" characters of the respective 

 seedlings. 



Table II. 



I 



Table II records the incidence of mildew during 1917, 1918 and 1919 

 on 14 seedlings growing in the 'hop-garden. 



We see that the seedlings Z 24 and Z 26, which grew on either side of 

 the "immune" Z 25 (and so closely that lateral shoots became inter- 

 twined) have each season^ become excessively mildewed. Similarly with 

 Z 41 and Z 43, on either side of, and as close to, the "immune" seedling 

 Z 42; and with OD 18 and OD 20 on either side of OD 19. 



We will now return to the consideration of Table I. Some further 

 data are available with respect to some of the plants there tabulated. 



The seedlings 316, OB 26, OE 14, DD 31 were subjected to the 

 severest test (as regards constant inoculation with coyiidia) in the green- 

 house during the seasons 1916, 1917 and 1918^. and all remained per- 

 sistently immune. On being planted out into the hop-garden in the 

 winter of 1918-19. two of the seedlings (316, DD 31) showed in the 



^ In 1916 also both plants were S3, while no mildew occurred on Z 25. 

 2 See (1), p. 456; (2), p. 88; (3), p. 252. 



