188 Studies in Bacteriosis 



and 5. They vary from a few spots developed near the calyx to many 

 scattered promiscuously over the surface of the fruit. They greatly 

 reduce the market value and in bad cases, as in Plate VIII, the fruit is 

 rendered quite unsaleable, being almost covered with these pock-like 

 depressions. 



Attacked plants become very brittle and are easily broken by the 

 workers. In the worst case the whole plant becomes covered with lesions 

 and finally dies. 



MORBID ANATOMY. 



Lesions in the pith and cortex are the characteristic internal features 

 of the disease, the walls of the attacked tissues are strongly browned so 

 that the patches are readily seen on splitting the stem with a knife. 

 Plate IX, fig. 2 shows rather advanced lesions in the pith of a stem and 

 fig. 1 shows a typical lesion in the cut petiole. In older stems which have 

 become hollow, small brown patches occur in the remains of the pith 

 and in the cortex but at the nodes where the pith is close and moist the 

 patches are much larger. Microscopic examination of the stem seldom 

 reveals the presence of the parasite in a living condition in these patches, 

 but the walls stain deeply with fuchsin and the intercellular spaces are 

 choked with deeply staining material strongly indicating bacterial 

 attack. The appearance of the diseased tissue is not that of a soft rot 

 though the middle lamella is partially destroyed. The cells appear to be 

 torn asunder by shrinkage of the dead cells and tension set up by growth 

 of the surrounding healthy tissue (see Fig. 3): eventually large cavities 

 are produced in this way. 



The roots are often found to be diseased only in the upper portion and 

 infection can usually be traced to some wound or insect puncture just 

 below the ground level; the tissues of the lower roots are in these cases 

 white and apparently healthy. In some cases, however, no wound can 

 be discovered, but the cortex is found to be browned to a considerable 

 depth below the soil level and microscopic examination shows the 

 presence of the bacillus in the tissue. It seems that penetration of the 

 root may occur without the aid of a wound, but of course there is always 

 the possibility that a small wound has escaped observation or again 

 that the disease has spread down to the root from an aerial infection. 



PVom the root the organism travels up the stem in the peripheral 

 parts of the pitli next to the proto-xylem elements. The organism is very 

 seldom found within the wood vessels themselves, and for some consider- 

 a))l(> time despite careful ex.nniiiatioii one could not demonstrate the 



