S. CI. Patne 09 



The symptoms of the disease and a very full account of it are given 

 by Smith (42). The disease was observed in England in 1901(30) and in- 

 vestigated by Potter (38) who isolated a Pseudomonas and in 'Ireland in 

 1910 by Johnson and Adams (in) who state that they isolated P. cain- 

 'pestris though their published evidence is insufficient to establish this 

 identity. Miss Doidge(i3) has found P. campestris in diseased cabbages 

 raised from English seed. 



The parasite. P. campestris is a short rod-shaped organism with 

 rounded ends, motile by means of a simple polar flagellum. 



Host plants. Practically all members of the Cruciferae are attacked 

 by this organism, cabbages, brussels-sprouts, turnips, swedes, radish, 

 rape, etc. 



Bacterial Blight of Fruit Blossoms. 



The blighting of pear and other blossoms and the consequent loss of 

 fruit has long been recognised as one of the worst evils with which the 

 fruit grower is beset. This had almost universally been considered to be 

 due to the effects of frost or of cold winds until the matter was investi- 

 gated by Barker and Grove (3). That these agencies, especially the former, 

 do cause a considerable amount of loss is indisputable, but probably the 

 greater part of the blossom blight is due to bacterial infection. The 

 bacterial origin of the disease was discovered in 1913 by Barker and 

 Grove who succeeded in obtaining in pure culture from diseased blossoms 

 an organism which readily reproduced the diseased condition when 

 placed upon or injected into various parts of flower buds borne upon 

 healthy young shoots. 



Symptoms of the disease. The first symptoms of disease vary con- 

 siderably in individual flowers according to the flower part first attacked. 

 Infection may take place in the sepals before the opening of the flower 

 bud. These first turn grey at the tips and soon commence to blacken 

 downwards towards the flower stalk : subsequent infection of this rapidly 

 leads to death of the whole bud. The same result is often to be observed 

 if the petals receive the infection, but in this case it frequently happens 

 that the attacked petals fall prematurely before the other flower parts 

 have become involved and the young fruit may then set normally. The 

 receptacle frequently bears the onset of the disease, and being an internal 

 structure the diseased condition is liable to be overlooked, the resulting 

 failure of the fruit to set being attributed to lack of fertilisation. Small 

 greyish-black spots appear which in a short time spread over the whole 

 receptacle and the disease is conveyed to the ovary. Finally, the disease 



