Arthur S. Horne and Eleanor Violet Horne 195 



1| ins. in diameter on April 11th and 2{ ins. in diameter on April 23rd; 

 in the case of Newton Wonder, small spots \ in. in diameter were present 

 on April 11th which increased to \ in. on April 23rd. In both cases 

 black, sterile perithecia of Pleospora developed in the diseased areas. 



A number of apples were inoculated with Pleospora pomorum while 

 still on the tree in August, 1917. A representative series of varieties was 

 chosen including two varieties, viz. Bismarck and Charles Ross, from 

 which this fungus had been isolated. 



The method adopted was as follows : two spot-free apples were chosen 

 of each variety and punctures made (using a sterile needle) in each; one 

 apple was inoculated with a minute fragment of mycelium bearing conidia, 

 and the other not inoculated. After inoculation the apples were enclosed 

 in manilla bags similar to those used in pollination experiments. The 

 apples, by design, were not sterilised before inoculation, as it was desired 

 not to injure the surface of the apple in any way. The inoculant was 

 therefore exposed to competition from fungi already present on the 

 apple. Records of the appearance, etc., were taken at short intervals. 

 As the apples ripened they were removed from the tree and stored under 

 suitable conditions. 



Of the 28 varieties inoculated, spots were not formed at the point of 

 inoculation in five, viz. the firm-fleshed russet — Court Pender Piatt, 

 Norfolk Beaufin 1 , Charles Ross 2 , Ribston Pippin and Cellini. Small spots 

 were formed which remained arrested for a period in seven varieties, 

 of which five are culinary sorts — Alfriston, Allen's Everlasting, Beauty 

 of Kent, Calville Boisbunel, Cockle's Pippin, King of the Pippins and 

 Lord Derby. The remaining 16 varieties developed "spotting" more 

 or less rapidly and rotting ensued — Allington Pippin, Belle de Pontoise, 

 Bismarck, Bramley's Seedling, Cardinal, Crawley Beauty, Duchess 

 Favourite, Early Victoria, Grenadier, Keswick Codling, Lane's Prince 

 Albert, Potts's Seedling, Red Astrachan, Rival, Royal Jubilee and 

 Wealthy. 



In the case of five of the 16 varieties which eventually rotted — 

 Allington Pippin (Jan 11th), Rival (Jan. 11th), Wealthy (Dec. 31st), 

 Royal Jubilee and Cardinal — Pleospora was re-isolated from the diseased 

 tissue. In the first four of these the development of spotting occurred 

 between Sept. 12th and the end of November, that is approximately 

 the time these varieties are in season. In the early variety. Cardinal. 



1 Large natural sjiots formed on the inoculated apples. 



2 The failure to infect Charles Ross is noteworthy, since Pleospora was isolated from 

 this variety on Oct. 25th, 1915. 



