VARIOUS CAUSES ASSIGNED FOR B1TTMR PIT. 



01 



tint on the side opposite the principal coloration, and, to all appearance, Bitter Pit had developed 

 (Fig. 59). But, on cutting it across, it was found that the depressions on the skin were due to a 

 Looper caterpillar tunnelling beneath, and, where it approached the surface, there was a depression 

 just as the surface soil might sink in when undermined. There was certainly no development of pit 

 in the absence of mosquitoes in the solitary apple borne by the netted tree, but the mosquito theory 

 does not by any means account for the facts, as already shown. 



FUNGI AND BACTERIA. 



ThAt the disease is non-parasitic in its nature is now agreed upon by all competent investigators. 

 The microscopic examination of hundreds of sections of pitted spots failed to reveal the presence of 

 fungi. From the investigations of Wortmann in 1892 down to those of Pole Evans in 1909, it has 

 been invariably found that neither fungi nor bacteria were concerned in it. 



In 1904 I forwarded specimens of pitted apples for bacteriological examination to Dr. Bull, 

 Bacteriologist of the Melbourne University, who reports as follows :— " My examinations of apples 

 forwarded on 28th March were largely of a negative character as regards the causal relationship of 

 micro-organisms to the diseased portions. Microscopic examination failed to demonstrate the 

 presence of any specific form of organism, and bacteria were for the most part very scanty. Very 

 few organisms developed on gelatine plates, and those present were principally moulds and 

 chromogenic air organisms. It may be of interest to note that the specimens of apples have been 

 kept in a cool room at a temperature varying from 32° to 45° C. since 28th March (four months). 

 On examining them this morning I found that most of them had completely softened, and were 

 covered with a copious growth of moulds, mainly Penicilliwn glaucum. Several of them, however, 

 although in direct contact with rotten fruit and copiously powdered with mould spores from adjacent 

 apples, were in a perfectly sound condition except for the presence of the original diseased spots. 

 The noteworthy thing Was that the original disease had not progressed. If the conditions were due 

 to bacteria per se, it is extremely probable that under such favorable conditions for pathogenic 

 action and re-infection all the apples would have been destroyed. The apples which survived were 

 Jonathans, and a large green apple with mottled red streaks (label lost). Several New York Pippins 

 were fairly sound." 



Professor Farmer, M.A., D.Sc, F.K.S., of the Imperial College of Science and Technology, 

 London, also bears out the same view in a letter to me, dated 16th September, 1909 :— " I had somo 

 apples sent to me to ascertain whether the disease was due to fungal or bacterial action. I came 

 to the conclusion that there was no such infection, but that the disease is physiological, i.e., 

 intrinsically due to pathological death of tissues. But it seemed to me to be useless to continue the 

 inquiry when we oould not try experiments, which, in my view, alone were likely to lead to the full 

 elucidation of the trouble." 



Dr. Erwin F. Smith, of the Laboratory of Plant Pathology, United States Department of 

 Agr iculture, informs me by letter that " I have never studied very thoroughly the Bitter Hot of 

 liiddwin fruit spot of apples, but the few examinations I have made led me to believe that it WAS 

 not due to bacteria." 



In Europe and America, Africa and Australia there is the same consensus of opinion that fungi 

 ami bacteria are not concerned in its causation. But there may be brown depressions on the surface 

 of apples likely, on a superficial glance, to be mistaken for Bitter Pit, and which are found swarming 

 with bacteria (Fig. GO). There are these important differences, however, from Bitter Pit, that the 

 depressions are more of the nature of excavations, and principally that there is no browning of the 

 tissue beneath the skin. These surface excavations are comparatively rare, as I have only found 

 them in a few Lord Wolseley apples, and the causal relation of the bacteria will he determined next 

 season if specimens are available. 



