New York Agricultural Experiment Station. 103 



served that the plants were very uneven in size.^' Some grew 

 vigorously while others, scattered here and there through the field, 

 were small and some of them were wilting in spite of the fact that 

 the ground was saturated with water. An examination of the 

 wilted plants showed the lower portion of the tap-root to be dead 

 and the fibro-vascular bundles in the stem blackened as in black 

 rot. If this bundle blackening was really due to Psciidomoiias 

 campcstris (which was proven in one instance) the plants must 

 have been infected through the roots. Tliis point will be further 

 investigated during the coming season. 



If root infection is as common as it appears to be it is a very 

 important factor in the treatment of the disease. Root-infected 

 plants can not be cured and no method of treatment which deals 

 only with -the parts of the plants above ground, such as leaf-pull- 

 ing or spraying, can give any protection against root infection. 



Infection occurs at base of Icaz'cs close to the stem. — One object 

 in removing afifected leaves is to prevent the disease from passing 

 down the fibro-vascular bundles into the stem where it is beyond 

 control. When infection occurs on the margin of the leaf at some 

 distance from the stem this is easily accomplished; but the writers 

 have found that infection often occurs on the basal portion of the 

 leaf within one or two inches of the stem and gets into the stem 

 before it is observed. (See Plate II.) 



Many cabbage leaves have no well-defined petiole. Toward 

 the base the stout midrib is bordered on either side by a narrow 

 strip (one-fourth to one inch wide) of thin leaf tissue. Infection 

 is as likely to occur here as on any other portion of the leaf and 

 is apt to be overlooked because the closely-overlapping leaves 

 hide it. In a few days the disease has gained access to the stem 

 and then its progress can not be checked. This is one of the diffi- 

 culties in the way of the successful application of the leaf-pulling 

 treatment. 



13 In this connection it is interesting to note Russell's observation (Loc. cit. p. 39) 

 that: '• In some cases where the plants were small the disease had established itself 

 in the stem, but in the majority of cases only individual leaves were afifected." This 

 was on September i, when the disease was "just beginning to make its appear- 

 ance.' Probably, the small plants had been infected through the roots and their 

 small size was the consequence of such infection. 



