E. M. DoiDGE 63 



Pathological Histology. 



The organism was most easily studied in the rind of affected fruit; 

 satisfactory preparations were obtained by fixing in hot acetic alcohol 

 and staining wdth Ziehl's carbol fuchsin and hght green. 



This is essentially a disease of the parenchyma, the lignified tissues 

 of the stem are not invaded, and the organism is not found in the small 

 fibro-vascular bundles in the rind. The bacillus does not cause hyper- 

 plasia. 



As has been stated, in the majority of cases infection takes place 

 through a wound ; the very slightest abrasion with a fine needle being 

 sufficient. No definite evidence has yet been obtained by inoculation, 

 that stomatal infections are possible, but in a number of sections, 

 particularly those through incipient spots on naartje rind, the location 

 of the bacilli strongly suggested that they had effected an entrance 

 through the stoma. (Plate X, a.) In such cases the stomatal 

 cavity was occupied by a mass of bacteria and the surrounding inter- 

 cellular spaces had also been invaded. The rods multiply very rapidly 

 in the intercellular spaces, until the latter become much distended 

 and bulge into the cell cavity. Considerable tension is thus set up 

 and eventually the wall gives way and the bacilli force an entrance 

 into the cell. 



The cell cavity soon becomes entirely filled, but for a considerable 

 time the remaining walls are intact so that were it not for the absence 

 of any intercellular spaces it would appear that the organism was 

 intracellular. The cell contents become disorganised and disappear with 

 the exception of the protoplasmic lining of the cell wall which contracts 

 slightly away from the wall and stains deeply .with fuchsin. The cells 

 at this stage consist of a central mass of bacteria surrounded by a 

 deeply stained sack of disorganised cell contents and then by the 

 partially destroyed cell wall. The staining reaction of the latter is 

 not altered. Finally the intervening walls give way and the tissues 

 become completely disorganised. (Plate X, c.) 



The oil gland is often completely filled with a vast number of rods ; 

 it was afterw^ards found that the organism grows extremely well in 

 the presence of orange oil and lemon oil. The cells surrounding the 

 oil glands are also very frequently attacked. 



