86 Disease of Fruit Blossom 



one type of organism, a rod-like bacillus, developing. After the necessary 

 trials to test purity, stock cultures were made, and material from these 

 was taken for use in infection experiments. The latter gave positive 

 results quickly and without any difficulty, the characteristic discoloura- 

 tion of the flowers following a few days after infection. 



It was thus soon demonstrated that the disease was bacterial in 

 nature ; and a detailed study of it was begun. Our work is still incom- 

 plete, the limited duration of the flowering season curtailing infection 

 experiments and other observations on the flowers themselves in a living 

 condition ; but it has been thought desirable to publish a preliminary 

 account of the disease rather than to defer it until the results of the 

 current season's work are available. The present paper is concerned 

 primarily with the general characters of this disease, which, so far as 

 we are aware, has not hitherto been recorded, and a description of the 

 causal organism. 



The Characters of the Disease. 



The nature of attack and the result vary considerably in individual 

 flowers ; but the two following forms are perhaps the commonest. 



In the one case the sepals are the first parts of the flower to show 

 signs of attack. Their tips turn grey and then begin to blacken. 

 When weather conditions favour the disease this blackening soon spreads 

 to the whole of the calyx and in due course down to and along the flower 

 stalk. The infection of the latter quickly leads to the death of the whole 

 flower bud. This mode of attack is common with young, unopened 

 flower buds. The flower bud blackens and shrivels up. In moist 

 weather it soon falls from the blossom truss ; but under drier conditions 

 it withers and dries up, remaining attached to the flowering shoot or 

 spur for weeks or even months. It is not uncommon to find in late 

 summer whole trusses of these blackened mummified blossoms still 

 on the spur. In cases where the whole of the blossoms of a truss are 

 affected, the consequences as regards the future history and fruiting 

 capacity of the spur bearing the truss are serious. The whole truss of 

 blossom eventually dies and falls off, leaving the spur as a bare stump 

 devoid of foliage. This stump may eventually die back entirely to the 

 point of its attachment to the branch carrying it ; and in such cases, 

 if numerous, the future fruiting capacity of the tree is seriously restricted 

 for several seasons at least, until new growth and fresh fruit spurs 

 have had time to develop, on account of the large stretches of barren 



