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A Tomato Canker 



are often so numerous and close together that they coalesce, forming 

 large, scabby areas several centimetres in extent. As the fruit ripens 

 the tissues round the infected areas remains green, forming a green rim 

 round the scabs which is conspicuous on the red fruit. The rifts in the 

 epidermis become extended in cases of severe infection and whitish 

 brown cracks are formed, many of them over 1 cm. in length and ex- 

 tending into unaffected tissue. These open the way for putrefactive 

 organisms and the fruit usually rots within a few days after ripening. 

 Thus the disease not only disfigures the fruit and reduces its market 

 value, but seriously affects its keeping qualities. 



Fig. 1. Early stages in leaf infection. 



Morbid Anatomy. 



In inoculation experiments tomato leaves and fruit readily became 

 infected without wounding, so that in all probability infection usually 

 takes place through the stomata. This was confirmed by an examination 

 of a large number of sections of spotted leaves : in the earliest stages of 

 infection the bacteria are to be found in the sub-stomatal cavity (Fig. 1 a), 

 and later make their way to the adjoining intercellular spaces. The middle 

 lamella of the cells becomes much swollen, and stains an intense red in 

 sections treated with carbol fuchsin and light green, the cells in the 

 surrounding healthy tissue staining green (Fig. 1 b). As described by 



