162 Forms of the Hop resistant to Mildew 



In the class S^, consisting of seedlings which have shown a medium 

 attack of mildew each season, we have 26 plants, or 8-93 per cent. 



In the next class, where the incidence of mildew varies in different 

 seasons from S^ to S^ — that is, from a trace of mildew to an attack of 

 medium intensity — we have 48 plants, or 16-49 per cent. In this class 

 an appreciable degree of resistance to the mildew begins to be shown 

 by 'some of the seedUngs, but it is in the succeeding classes that this 

 phenomenon is most clearly seen. One seedhng, however, in the present 

 class proved to be commercially resistant. 



In the class S^, i.e. those seedhngs which have shown only a trace of 

 mildew each season, we have 12 plants. Of these, 5 cannot be considered 

 to have been sufficiently tested, leaving us with 7 seedlings which have 

 proved to be persistently resistant in the open. Among these 7 seedlings, 

 there are 4 which are immune, and 1 semi-immune, under greenhouse 

 conditions. 



In the class 0-S^ we have 9 seedlings, of which 1 has been insuffi- 

 ciently tested. These 8 seedUngs are "commercially resistant" in the 

 open; 5 of them are immune, and 1 semi-immune, under greenhouse 

 conditions. 



In the class 0-S^ in which there are 18 seedhngs, 2 plants (both of 

 which show immunity in the greenhouse) have proved to be "com- 

 mercially resistant" in the open. The other seedlings in this class, while 

 certainly showing resistance to the mildew, are liable to fairly serious 

 attacks in some seasons, and therefore cannot be considered as "com- 

 mercially resistant." Among these are 2 seedhngs which are immune, 

 and 1 which is semi-immune, under greenhouse conditions. 



The 13 seedhngs in the classes to S" and S^ to S^ do not constitute 

 in either case a proper group. Of the 3 seedhngs showing to S^, one 

 only possesses probably a shght degree of resistance. Of the 10 seedhngs 

 showing S^ to S^ in different seasons, 9 almost certainly belong to the 

 S^ or S^ class, while the remaining plant is OR 38 (immune in the green- 

 house), which is fully discussed above (p. 154). 



As constituting the group, then, of "commercially resistant" plants, 

 we have the following 18 seedhngs (representing 6-19 per cent, of the 

 291 ? seedlings), distributed in the following classes: 



SI to 82; OA34. 



OtoS^: Z20, Z22. 



gi: OC 25, OD 17, OE 14, FF 9, HH 20, HH 44, II 13. 



to SI : V 91, Z 25, OA 49, OB 34, OD 19, OY 24, BB 5, HH 9. 



