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EXPERIMENTS WITH A VIEW TO CONTROLLING THE DISEASE!. 109 



The experiments have at least one advantage, apart altogether from their bearing on Bitter 

 Pit, that each one of them will throw light upon a number of horticultural practices which aim at 

 the production of good yields and high quality. They will also advance our knowledge of 

 cultivation, manuring, pruning, stocks, irrigation, and cold storage in relation to fruit production 

 and keeping quality, and be for the general benefit of the fruit-growing industry of Australia. 



I cannot sufficiently express my appreciation of the facilities afforded in each State by the 

 Heads of the respective Agricultural Departments in furtherance of the objects of this investigation. 

 Each one seemed to vie with the other in assisting me in every possible way, and I was made to 

 feel, when visiting each State, that I was regarded as an officer of that Department for the time 

 being, seeking to benefit the fruit industry of the Commonwealth as a whole. The services of the 

 horticultural experts were also freely placed at my disposal, so that the investigation became more 

 of a co-operative undertaking than merely one of individual effort. 



Mr. C. C. Brittlebank, of the Vegetable Pathologist's Branch, Victoria, has been of great 

 assistance to me in the Laboratory, and has supplied the great majority of the striking photographs 

 here reproduced. 



To the horticultural press I also owe a debt of gratitude for the sympathetic tone adopted, 

 and for contributions on the subject of practical interest. 



And, lastly, I am indebted to Messrs. Cuming, Smith and Co. for gratuitously supplying 

 all the manures required for experimental work. 



SUMMAKY. 



It is a fundamental principle of pathology that the normal structure and functions of the 

 part or organ concerned should be determined as far as possible, in order that the abnormal 

 conditions may be properly understood. 



The structure and functions of the apple and pear were therefore investigated, with the result 

 that, on the removal of the skin and flesh after softening, there remained a delicate skeleton and 

 vessels as a model of the whole, ramifying through and permeating every portion of the fruit, 

 supplying the seed-vessels and the flesh with liquid nourishment, and forming a network of vessels 

 immediately beneath the skin. This vascular network was found to originate in the earliest stages 

 of the fruit, and continues to expand with the enlarging flesh. 



It is shown that neither insects nor fungi, bacteria, nor external agencies, such as spraying, 

 are concerned in the production of Bitter Pit. 



Bitter Pit is seen to be an internal disease, due to internal causes, and always found associated 

 with the discoloured vascular bundles. 



" Crinkle," or " Pig Face," or M Hollow Apple " is shown to be a confluent form of Bitter 

 Pit, every gradation being observed from pit to slight and advanced crinkle. Large cavities are 

 formed by the rupture of the tissue, owing to rapid and excessive growth at the periphery. 



Diseases found associated with Bitter Pit were " Black Spot," " Bitter Rot," " Glassiness " 

 or " Water Core," and " Mouldy Core." 



Appearances mistaken for Bitter Pit were hail-marks, bruised skin, effects produced by 

 chemical reagents, and local poisoning. 



Pitted Apples are produced on unsprayed trees, and a chemical analysis of such apples 

 revealed no trace of mineral poisons. 



It was found, as far as my investigations go, that the key to the solution of the* Bitter Pit 

 problem lay in the wonderful vascular system which permeates the " core " and the " flesh," and 

 the marvellous network of vessels just beneath the skin, their function being to regulate and equalize 

 the distribution of food material at the periphery of the fruit, where the greatest and most rapid 

 growth normally takes place. 



The brown spots of Bitter Pit are generally first formed in the^zone occupied by the vascular 

 net, of which there is not only ocular demonstration in the position of the tough brown spots still 



