S. a. Jones 293 



lopped off the foliage only to discover tiiat the roots were bad. A diseased 

 root cut in vertical section showed a Hask-shaped, soft, putrid core 

 surrounded by a brown zone abutting on the healthv tissue (Fig. 1). 

 The disease never made further progress into the rind nor into the lower 

 part of the root and this would therefore account for the healthy turges- 

 cent appearance of the fohage since the vascular tissue in the root and 

 rind would still be functional. Such were the external features of most 

 of the diseased jilants but in addition numerous cases were found where 

 the entire apical bud had been destroyed thus forming a large wound 

 only however to be concealed by no fewer than three, often five secondary 

 crowns all bearing healthy luxuriant foliage (Fig. 2). There were also 

 found numerous diseased roots with all foliage intact, but bearing deep 

 cracks in the rind above ground; these were probably examples of 

 "burst" roots a condition frequently found in sappy roots exposed to 

 sudden weather changes. In all these types however the internal appear- 

 ance of the diseased roots was precisely the same — the soft-rot was 

 always confined to the core of the root and in addition there was always 

 present the brown-coloured zone at the boundary of the diseased area. 

 A white-rot of turnips similar to the one now described has been attri- 

 buted by Potter to an organism Pseudomonas destructans (Potter). He 

 states that plants attacked by this parasite "can be recognised by the 

 drooping yellowish leaves, the older leaves being tlie first to show any 

 indications of disease; they gradually flag and droop to the ground, at 

 the same time becoming yellow and shrivelled in appearance. The leaves 

 next in age gradually exhibit the same signs of premature decay and this 

 proceeds until finally the young leaves at the growing point succumb; 

 the entire rosette of leaves perishes, and the whole root becomes a soft, 

 putrid mass, which eventually collapses etc." In the present disease, 

 however, the external appearances of the diseased plants showed features 

 very different from those accompanying the one described by Potter 

 and these were deemed sufficiently striking to warrant further investi- 

 gation. 



It has been a matter of extreme difficulty to detect the initial mode 

 of attack of this disease on the plants in the field. The writer has not 

 been able to investigate this important point and the evidence gathered 

 from the farmers is most conflicting. One noticed that the turnip plants 

 were to all appearances dead, with the leaves flat on the ground as if 

 the cattle had been lying on them but that on a subsequent visit he had 

 found the crop to all appearances fully recovered only to find however 

 at the time of harvesting that the roots were bad. Another said that 



