450 Journ<il of Agriculture, Victoria. \ 11 Aug., li)-li). 



in colour, and when an advanced stage of deterioration is readied they 

 become withered and shrunken. 



Usually William's Favovmte is the first of the early varieties tc 

 show Bitter Pit on the trees This occurs about the middle of 

 January, and the identification marks may be traced through the other 

 varieties in their order of maturing until the Sturmer Pippin, the last 

 of the late ripening sorts, becomes affected about the middle of May. 

 The fruit of trees making rank growth on rich, imperfectly drained , 

 }et, not absolutely sour soils is more subject to Bitter Pit than that 

 produced on trees of moderate growth on the lighter sweet soils. Under 

 either set of conditions excessive rain or unusual atmospheric humidity 

 seems to intensify the pitting, but more so in the case of the former. 



On completing his exhaustive investigation, of this matter on behalf 

 of the Federal Government, Mr. D. McAlpine in his fifth report (p. 60) 

 concerning the caiise of Bitter Pit states :' — 



■' I am of opinion that over-pressure of water in the tissues, 

 leading to local rupture and subsequent death of the parts, 

 furnishes the most probable explanation of Bitter Pit." 

 In page 66 of the same report, in further explaining his theory, 

 Mr. McAlpine writes: — 



" The result of this investigation goes to show that the primary 

 cause of the trouble is the extra pressure of sap in the outermost 

 layer of pulp eells to begin with, causing them to burst and 

 collapse, together with the rupture of the vascular network 

 associated with them. A large number of well-established facts 

 have been brought forward to support this view, which has sug- 

 gested the best known means of reducing the amount of pit in the 

 orchard, and these remedies are supported by experimental 

 evidence." 

 Simultaneously with Mr. McAlpine's investigations Professor Ewart 

 conducted a number of highly scientific experiments with a view to 

 determining the cause of the disease, and he claims that the results 

 obtained indicate that the condition of the pitted parts of the fruit 

 IS consistent with local poisoning. 



The nature and results of the experiments were embodied in a 

 series of papers read before the Koyal Society of Victoria, and subse- 

 quently published as pamphlets. The following extract is taken from 

 the pamphlet issued September, 1917, wherein the Professor states: — 

 " Every symptom of this defect can be produced by the arti- 

 ficial application of poisons, including the presence of starch grains 

 in the dead cells. 



Various obsei'vers have noted similar results in the leaves and 

 ^ young stems as the result of the application of poisonous sprays 

 (patches of dead tissues with brown shrivelled cells packed with 

 starch). In apples* the sensitivity is so great that the poisoning 

 may be oligodynamic, i.e., poisoning may occur in the presence of 

 traces of poison beyond detection by ordinary chemical analysis. 



As ii])ples ripen the sensitivity of the \n\\\^ cells to poison in- 

 creases, so that the apparently sound apple may develop Bitter Pit 

 after it has been picked. 



There is a close correspondence . between resistance to 

 poiison and resistance to Bitter Pit. The most re- 



