6lO JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Table III. — Experiments with Potato ' Duke of York.' 



Result of examination of tubers from January 20, 1913, to April 1913. 





















Percentage 





ference 

 etter 



jmber 

 tubers 

 imined 



:eak 



yto- 

 thora 



atch 



y rot 





:eak ^ 



yto- 

 thora 



otch I 

 / 



y rot 



* 



■a 



ar 









s 



H 



p 







a, 0. 



5 



Q 



O 

 H 



A 

























C 





















— 





B 



100 



2 



0 



0 



2 



4 



2 



O 



0 



2 



4 



D 



432 



O 



8 



0 



3 



11 



O 



2 



0 



I 



3 



E 



264 



O 



16 



4 



4 



24 



O 



6 



i-5 



i'5 



9 • 



F 



528 



O 



2 



21 



33 



61 



O 



O 



4 



7 



11 



Let us now survey the total results of the whole experiment dis- 

 played in Table IV. We have first of all a small percentage of blotched 

 tubers amongst those grown from the disease-free sets presented 

 by Messrs. Sutton (lots E and F). The marks consisted chiefly of 

 brown spots, specks, and blotches, and did not take the form of streaks 

 such as appeared in the same variety when grown in Scotland. The 

 tubers in question were mainly confined to the produce from washed 

 sets : there being only four cases among the 404 tubers derived from 

 the unwashed sets. 



The yield from the diseased sets was very poor, as shown in Table I., 

 due to the fact that many of the sets produced poor plants or entirely 

 failed. Streak appeared among the tubers originating from these sets 

 as in all my previous experiments conducted elsewhere : but only six 

 out of a hundred tubers produced by unwashed sets were affected, 

 whereas there were 39 cases among 258, or fifteen per cent., in the 

 produce from washed sets. 



An exactly opposite result was obtained with lots B and D. The 

 tubers used here as well as those in lots A and B were chosen, it will 

 be remembered, from the potatos raised on land that produced a 

 crop affected with streak in the previous year. The produce from the 

 washed sets yielded not a single case of streak and only eight cases of 

 Phytophthora among 638 tubers examined, whilst the produce from 

 the unwashed sets yielded 13 cases of streak and three of Phytophthora 

 among 380 tubers. 



Table IV. — Experiments with Potato ' Duke of York.' 



Total result of examination of tubers from September 1912 to April 1913. 



Reference 

 | letter 



Number 

 of tubers 

 examined 



Streak 



Phytophthora 



Blotch 



Dry rot 



Total 



j 



Phyto- 

 phthora 



Percentage 



Total 



A 



IOO 



6 



O 



0 



O 



6 



6 



O 



0 



0 



6 



C 



258 



39 



9 



0 



O 



48 



T -5 



3' 5 



0 



0 



iS-5 



B 



380 



13 



3 



0 



2 



18 



3-5 



1 



0 



•5 



5 



I) 



O3S 



0 



8 



0 



3 



1 1 



0 



1 



0 



5 



1 '5 



KE 



404 



0 



!? 



4 





33 



0 



0 



I 



1 



8 



11 



712 



0 



! 13 



37 



>- 



90 



0 



2 



5 



5'5 



13 



