lof^ Forms of the Hop resistant to Mildew 



to the extent of S^, S^ and S^ in those years respectively. In the green- 

 house, 35 cuttings of OR 39 have all proved persistently immune when 

 tested in various seasons. 



Ref. no. OY 18. No mildew was present in 1918; a trace of mildew 

 occurred in 1919 and 1920. The behaviour of its neighbours on either 

 side was as follows: OY 17 (?), 1918, S^. 1919^ gi. qY 19 (?), 1918 and 

 1919, S3. 



Ref. no. DD 31. A trace of mildew occurred in 1919, which was the 

 first season after the seedling had been planted out in the open. As a 

 young non-flowering plant it remained persistently immune in the 

 greenhouse for three consecutive seasons (1916-17-18). In 1920 no suit- 

 able material for infection was present in the hop-garden in the autumn. 



Ref. no. HH 20. This seedling showed a trace of mildew in 1918. Its 

 neighbour HH 19 (?) was S^ in 1918, and its other neighbour HH 21 {$) 

 was S^. No suitable material was available in 1919, and the seedUng 

 was then grubbed up for want of room. 



Ref. no. HH 44. A trace of mildew occurred on this seedhng each 

 season from 1917 to 1919; in 1920 no suitable material was available. 

 Its neighbour HH 43 (?) was S^ in 1918 and 1919. 



Ref. no. II 13. In 1918 a minute patch of mildew occurred on one 

 leaf only. No suitable material was available in 1919 and the plant was 

 then grubbed up for want of room. 



Ref. no. II 24. No mildew occurred on this seedhng in 1918 and 

 1919; its two neighbours, II 23 (?) and II 25 (?) were both S^ in 1918. 



Ref. no. II 30. In 1918 this seedhng remained free from mildew, 

 although a lateral shoot of II 31 {$) which was virulently affected with mil- 

 dew twined round it. No suitable material was available in 1919 and 1920. 



Ref. no. 316. A minute trace of mildew occurred in 1919 and in 

 1920 — in the latter season the small patches of mildew were confined 

 to the undersurface of one leaf only. 



Summarising the histories of the 27 seedhngs which are immune in 

 the greenhouse we find that 5 seedhngs (Z 2, Z 17, Z 42, II 24, II 30) 

 have remained immune in the hop-garden. All these are $ plants and as 

 such have been less severely tested under the special conditions noted 

 above (p. 149) than the ? seedlings; further, two of them (Z 17 and II 30) 

 have obviously been insufficiently tested. Taking the evidence as a 

 whole, one is led to the conclusion that in all probabihty these five 

 seedlings need only some particular weather conditions, coupled with a 

 certain stage of growth, to show in the open at least the S^ stage of 

 susceptibihty. 



