E. S. Salmon and H. Wormald 263 



In the class — *S'^ wo have 9 seedlings, of which 1 has been in- 

 sufficiently tested. Of the remaining 8, 6 are immune, and 1 semi-immune, 

 under greenhouse conditions. 



In the class — *S-, in which there are 18 seedlings, 2 plants (both 

 of which show immunity in the greenhouse) have proved decidedly re- 

 sistant in the open, the grade of infection only very rarely I'eaching to S". 

 The other seedlings in this class, while certainly showing some resistance 

 to the mildew, are liable to fiiirly serious attacks in some seasons. 

 Among these seedlings are 2 which are immune, and 1 which is semi- 

 immune, under greenhouse conditions. 



The 13 seedlings in the classes — S'-^ and *S'' — S'^ do not constitute 

 in either case a proper group. Of the 3 seedlings showing — *Si', one 

 only probably possesses a slight degree of resistance. Of the 10 seedlings 

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

 or S'^ class, while the remaining seedling, OR 88, which is immune in 

 the greenhouse, is exceptional in showing in the open as high a grade of 

 susceptibility as *S'^ in some seasons. 



The degree of susceptibility to mildew shown by the seedlings has 

 no correlation, so far as we can see, with other characters. Thus among 

 the resistant plants are some with green bines others with red bines, 

 some are early, others late, some have many glands, others few, and 

 similarly with the very susceptible plants. Again, plants Avhich are in- 

 distinguishable in other ways show different powers of resistance towards 

 the fungus as shown by the following records : 



Description of plants 



^ very early, green bines, many leaf ]Z17 — — — — O — O 

 glands, few perianth glands, rather ■Z42 — — O — O 

 pale leaves J 0G4 — — S- — S'' — S' — 



$ late, red bines, few leaf glands, ) ^ . An n S^ 



condition fair, aroma pleasant,^ ^-r. ^ „;j ,^3 03 ct. 



strig red 



5midseason, red bines, few leaf 

 glands, condition poor to fair, strig 

 red (aroma generally more pleasant 

 in OD 19 than in OD 16) 



$ late, red and green (mottled) bines, '\ 

 many leaf glands, condition fair I Z 22 O — S^- S" O S^ or S- O 

 to good, aroma pleasant, strig red- [ OG28 — — -S* — S'' — .S*t — 

 dish with darker nodes j 



As regards 'the characters taken, then — which comprise the most 

 important morphological ones — for many (if not all) of the " immune " 

 forms there appear to be susceptible forms which are similar morpho- 

 logically. It is to be noted that similar forms in other species of plants 



OD 19 o — o .51 o ,51 o 

 0D16 S-^ — S-^-f — S^ S .S-t S 



