E. S. Salmon 255 



to be susceptible to a slight extent, several of the leaves and one hop 

 (strobile) being slightly affected. In 1917, in October, there Avas a fair 

 amount of mildew (with perithecia) on the hops; and in 1918 by Sept. 

 7t^ there was a fair amount of mildew on the young leaves and by 

 October the hops had become excessively mouldy, a considerable 

 percentage of them being deformed or totally undeveloped owing to the 

 attacks of the mildew. 



During the winter of 1916 17, five "cuts" were taken from OR 38 

 and grown (in pots) during the season of 1917 in the greenhouse; these 

 "cuts" proved to be immune, except that two of them showed a tempo- 

 rary and strictly local susceptibility i. Two of these five "cuts" taken 

 in 1916-17 were kept in the greenhouse during 1918, and proved per- 

 sistently immune. The remaining three "cuts" had been planted out, in 

 the autumn of 1917, in the hop-garden, and, as young, non-flowering 

 plants, all proved in October, 1918, to be susceptible. One plant 

 (Ref. No. W56), l|ft. high, showed a fair amount of mildew on the 

 leaves; one plant (Y 28), 5 ft. high, was very mouldy on the leaves and 

 stems; the third plant^ (Z 4), 5 ft. high, was very mouldy on the leaves. 



During the winter of 1917-18 nine " cuts " had been taken from OR 38 

 and these were grown in pots in the greenhouse during 1918. These plants 

 proved persistently immune, notwithstanding the fact that the parent 

 plant was decidedly susceptible in the hop-garden both in 1917 and 1918. 



Plant 11. Ref. No. OR 39 (J 

 1914 G (I), 



1916 H(Si), 



1917 H (SI); 2 "cuts" 1916/17 G(I), 



1918 H(?I); 2 "cuts" 1916/17 G(I); 6 "cuts" 1917/18 G (I). 



This seedling, after proving immune as a 2-year-old seedling in the 

 greenhouse in 1914, showed slight susceptibility in the hop-garden in 

 October, 1916, one leaf each on two lateral shoots showing small patches 

 of mildew. In 1917, in October, there was one small patch of mildew on 

 the under-surface of one leaf of a lately-developed lateral shoot. In 

 1918 there was no mildew on the plant; as, however, no actual inocula- 

 tions were made the immunity cannot be held to be definitely proved. 

 During 1916-17 two "cuts" were taken from OR 39; these proved 

 immune in the greenhouse for two consecutive seasons. Six "cuts" 

 taken in 1917-18 proved immune in the greenhouse during 1918. 



^ The facts have been given in detail, and discussed, in (2), p. 84; 86. 

 - This was the "cut" which in 1917 has proved immune, in the greenhouse, in the 

 Exper. 4 recorded in (2), p. 85. 



17—2 



