Cucumber and Tomato Canker. [oct., 



change to an ashy-grey or whitish colour, and the epidermis 

 becomes broken up and studded with numerous perithecia 

 belonging to the conidial stage of the fungus. This is fol- 

 lowed by the production of the ascigerous condition of the 

 fungus when the host is dying or dead. Infection experi- 

 ments proved that the spores of the fungus could infect 

 uninjured melon plants, also other allied plants, although, 

 curiously, the cucumber proved immune, and resisted all 

 attempts at infection in the United States. 



Quite recently specimens of diseased tomato plants were 

 received at Kew from Waltham Cross. In each case the base 

 of the stem was considerably shrunken, and the cortex de- 

 stroyed, and studded with numerous minute perithecia, which 

 on examination proved to be identical with the conidial or 

 Ascochyta stage of the American melon disease. In some 

 specimens the nodes of the stem were also attacked. Plants 

 attacked as above promptly succumbed, a grower's state- 

 ment being that they fell over like nine-pins. 



Almost simultaneously with the above, a diseased cucum- 

 ber plant was received from Gloucestershire, which showed 

 the whitish diseased nodal portions of the stem, characteristic 

 of the American melon disease. Numerous minute perithecia, 

 which proved on examination to be those of the Ascochyta, 

 were present on the diseased patches. 



Cucumber plants attacked by this disease are stated to be 

 quickly killed outright. Experiments conducted at Kew 

 showed that the spores from diseased cucumber plants infect 

 young tomato plants, and that spores from a tomato plant 

 would infect vegetable marrow plants. In both instances the 

 plants infected showed the conidial (Ascochyta) stage of the 

 fungus within a fortnight, and in both instances the lesions 

 formed were characteristic. 



Both in this country and in the United States the conidial 

 form of fruit is responsible for the rapid extension of the 

 disease. 



The simultaneous occurrence of this well-known American 

 disease at two widely separated localities in this country is 

 difficult to explain, as living melon plants are not imported, 

 and the fungus does not attack the fruit. 



The result of preventive experiments conducted in this 



