A. S. HORNK AND H. M. Lefroy 



383 



In the following year there was a recurrence of the phenomena 

 already mentioned, whilst again certain races remained quite healthy 

 nevertheless, the foUage of almost every plant of other races was bad y 

 diseased. The whole question of the disease ^^^^ ^^ ^ T . n to a^ 

 cannot be discussed here, since it must be considered m relation to all 

 the conditions under which the races in question were raised and grown. 

 Three types of injury could be distinguished : -,.•,. 



1. Blotched foUage not associated with discoloured vems, neither 



insects nor their remains present. . , ,. i i ,.. .r.,\ 



2. Badly blotched fohage associated with discoloured veins and 



/ V^ Blotched fohage associated with the presence of Capsids. 



A great deal of the damage was certainly due to a secondary extension 

 of the injuries primarily caused by insects, owing to a period of bad 

 weather following the mfestation. Coccinella was not present m 



^^""Ckind permission of Messrs Sutton, the firm's potato trials at 

 Reading were visited in 1912. The plants were remarkably free from 

 bllishl of any kind and on several varieties, notably "J;— 

 and Maincrop, no injuries due to insects could be ^e -te^ a^ ,^^^^^ 

 Amongst plants of Windsor Castle only one was infested w^th JLph- 

 Several plants of the Up-to-Date had been attacked and showed the 

 'Z:^J^^.o.. veins. Curiously enough the Up-to-Dates wei. 

 adjacent to other varieties from which insect mjuries were absent. 

 Coccinella was abundant. 



Field observations on Capsids. 

 The President plants grown at Wye in 1911 were practically free 

 from insect injuries, but they were also free from blotches o;"««j 

 leins On July 30, 1912, Professor Theobald informed us that he had 

 Observed nothing but a few Aptera and some Capsids on potato plants 

 at Wve in that year. _ ,, 



The plante raised at the Chelsea Physic Garden ,n 911 were badly 

 blotched and it is now quite clear that the condition of the fohage was 

 due to Capsids. On June 28, 1912, the plants grown from tubers in 

 the open at Chelsea were more carefully examined for insects. Several 

 plants had been injured by Capsids and many Capsids were observed^ 

 The first Capsids used for experimental purposes were captured at 

 Wisley on June 11, 1912. This was almost their earhest appearance 

 at Wisley On June 17 Capsids were active at Oxshott, especially on 



