VARIOUS CAT'SIiS ASSiaXEl) FOR bitter pit. 



59 



As regards the theory of rapid evaporation of moisture from the surface, of the frui^ 

 causing the disease, this was the explanation given concerning some apples affected with Bitter 

 Pit forwarded to the United States Department of Agriculture some fourteen or fifteen years ago. 

 Mr. Robin, of Nuriootpa, South Australia, sent some specimens of Esopus Spitzenberg apples, 

 badly affected with Bitter Pit, and the Chief Pathologist suggested that it might have been caused 

 by sun scald, the hot sun having burnt the spots on the skin of the apples, upon which dew-drops 

 had collected. 



Massee (54) has shown that spotting of the leaves may be brought about by minute drops 

 of water on their surface at a time when the temperature is exceptionally low, and the roots 

 copiously supplied with water. A chill is thereby produced, which affects the underlying cells, 

 and so causes the "spot." But Massee himself, in discussing Bitter Pit, does not explain it in 

 this way, when the fruit of the apple is affected. 



Lafar (47), in the English translation of his Technical Mycology, in 1898 attributes the 

 "brown spotting" of the apple, that is the spotting of sound apples under the rind, to some 

 mechanical action. Whenever the cells become ruptured, from the dropping of the apple from 

 the tree, or pressure in packing or transit, for example, then the oxygen is afforded an opportunity 

 to act on the exposed constituents of the plasma. The enzyme found in the apple by Lindet 

 (108), in 1893, carries the oxygen to the tannin, and the result is that dark-coloured oxy-compounds 

 are produced, which are precipitated on the cell-walls as a permanent dye. This view does not 

 explain the development of the brown spotting while the apple is still growing, and attached to 

 the tree, where external mechanical agencies are excluded, from the very nature of the case. 



UNFAVORABLE CONDITIONS OF SOIL AND CLIMATE. 



Since the fruit is the outcome of all those antecedent conditions which affect the healthy 

 growth of the tree itself, it will readily be understood that the nature of the soil and of the climatic 

 conditions will have an important bearing on the formation of properly-matured and fully-formed 

 fruit. The temperature of the soil, together with the necessary supply of air and food and water 

 through it, will be dependent largely on its character, whether of a light and porous texture, or 

 heavy land, with too much clay, and the rainfall, drainage, irrigation, &c, will all have an 

 influence on the result. In Germany it is stated by Sorauer (85) that it is most common on loose 

 soil in dry years; the general opinion of growers there is that a wet summer, with little sun, 

 encourages it. Tn England it is said to occur with alternations of sun and shower, and even with 

 heat and drought, as in 1911. Tn Australia (as we have seen) the prevailing opinion is that a wet 

 season favours the disease, although a few have found it in dry years. 



Whatever interferes with proper root-action, whether soil or climate, will affect the water 

 supply, and, since it is known that excessive transpiration is favorable to the production of 

 " pitting," there is bound to be a. close interaction between the tree and its non-living environment, 

 resulting in a normal or abnormal growth of the fruit. Manuring, to supply any deficiency in 

 the soil, pruning, to regulate the proper distribution of fruit on the tree, and methods of 

 cultivation, to control the due supply of heat and moisture, will all tend to minimize the effect of 

 otherwise unfavorable conditions. 



INSECTS. 



As showing how hopeless were the early attempts to account fur this disease, and how- 

 superficial the efforts to connect cause and effect, the theory of insect punctures is a striking 

 illustration. 



The common Harlequin Hug (Dindyi)ius versicolor), which is a native of Australia, and maybe 

 found at certain seasons in countless myriads on almost any weed, or even fruit, was supposed to 

 puncture the skin of apples, to extract the juice, and cause the fruit to spot. It often causes 



