3*2 Studies In Bacteriosis 



example of the cholera bacillus, in the bacteriolytic serum of an im- 

 munised animal.) This view is supported by the fact that in sections of 

 some of the spots bacteria cannot be definitely recognised, and further 

 by the fact that when attempts are made to isolate the parasite many of 

 the spots appear to be sterile. A somewhat similar pathological condition 

 has been described by Potter^ in a brief account of a raised leaf-spot 

 disease of an orchid, Odonfoglossum Uro-Skinneri; the swelling of the 

 tissue is there attributed to the production of a mucilaginous substance 

 in which bacteria, believed to be the cause of the disease, are found 

 embedded. It is possible that the substance is of the same nature in 

 both cases, but in Odontoglossum it is described and figured as occupying 

 the intercellular spaces while in Protea it is found only within the cells. 



Some attempt was made to determine the nature of this substance 

 in Prolea, but unfortunately the amount of material available was too 

 limited to permit of any extensive investigation of the part it plays in 

 the bacteriolytic process or of its chemical composition. First it should 

 be noted that the presence of this substance is not confined solely to the 

 diseased areas, but appears in its structureless non-staining variety 

 wherever the tissues are wounded and also in certain cells in tlie neigh- 

 bourhood of the vascular bundles. It may perhaps be an ordinary tannin 

 product of the host cells and, if the assumption of bacteriolysis is correct, 

 may serve in the diseased area simply as a vehicle in which the solution 

 of bacteria is brought about by some other agency, possibly by autolysis. 



The gummy substance becomes very brittle in fixed material, and in 

 consequence it has been found very difficult to prepare good sections of 

 the diseased tissue, and almost impossible to obtain microtome sections. 

 The irregularities and the fissures in the substance depicted in Figs. 3 

 and 5 give some idea of its mechanical texture; the material from which 

 the sections here shown were prepared had been preserved in weak 

 formahn. 



Fig. 3 was drawn from a very imperfect microtome section typical 

 of several attempts to cut the material on the microtome; with the 

 exception of one of the epidermal cells only fragments of the tissue were 

 obtained in spite of the fact that the cuticle, itself a difficult subject for 

 the knife, was cut perfectly. The epidermal cell referred to, presumablv 

 recently invaded by bacteria, possessed a matrix of a scarcely perceptible 

 yellow tinge, while the contents of many of the neighbouring ceils were 

 deep yellow to dark amber in shade^. This is taken to indicate that the 



* Gardeners' Chronicle, Ser. in, vol. 45, p. 145. 190it. 



'^ The bacterial stain omployod in this case was Viotoria blue, not fuohsin. 



