THE CAUSE OF BITTER PIT. 59 



They were placed in the Government Cool Stores, Melbourne, on 1st March, and removed for 

 examination on 4th May, being kept at a temperature of 31 degrees Fahr. The fruit was found to be 

 in the same condition of ripeness as when placed in store, and perfectly sound, without any traces of 

 decay. 



There were four cases altogether, one from each of the trees used for pruning experiments, and it 

 was found that the worst samples of Pit were obtained from the severely pruned trees. The results 

 of the examination showed that while there were from three to four apples pitted in each fruit case, 

 only in one of them was the pitting sufficiently decided to attract attention, and the pits were invariably 

 at the calyx end of the apple. 



The following table gives the results according to the method of pruning adopted : 



TABLE XXXV. 



No. 1. Severely Pruned J29 apples in case, with 3 decidedly pitted and several with one to two 



pits at most. 



No. 2. Lightly Pruned 137 apples, with 1 showing one pit. and two, three pits respectively. 

 No. 3. Leader ,, 153 apples, with 3 showing one, two, and three pits respectively, and a 



fourth with six pits. 

 No. 4. Unpruned . . 154 apples, with 3 showing one pit each, and one with two pits. 



It may be remarked that, although the apples showed no visible sign of Bitter Pit when stored, 

 yet there may be some with Bitter Pit latent when examined under the X-rays. Such apples may 

 develop it to a slight degree, even under cold storage conditions. 



THE CAUSE OF BITTER PIT. 



Wherever apples are grown on a commercial scale this disease is more or less prevalent. In 

 Australia there are some valuable export varieties, such as Cleopatra, which are so susceptible that 

 they have been cut down and replaced by other varieties. In the United States of America the 

 Baldwin variety is so subject to attack that the disease is actually known as "Baldwin Spot." In a 

 recent American publication it is stated that "unless a remedy for this trouble is to be found, the indica- 

 tions are that Baldwins will sooner or later need to be replaced by some other variety of the same 

 season and quality which is not affected by the spot." There is consequently a keen desire on the part 

 of growers to know the cause of the disease, in order, if possible, to devise measures for its prevention 

 or mitigation. By this means alone may certain valuable varieties be retained under cultivation. 



In my previous Report I have offered alternative views as to the cause of Bitter Pit, viz.: 



(a) Concentration of cell sap in the tissues of the apple and consequent local death of the 



parts. 



(b) Over-pressure of water in the tissues, leading to local rupture and subsequent death of the 



parts. 



The first explanation was indicated by certain of my observations. The brown flecks of the 

 Pit, when examined, always contained less water than the surrounding healthy tissue, and it appeared 

 possible that the concentration of the cell sap involved in loss of water might have reached a point 

 where the acids, tannins, and other constituents acted injuriously upon the living protoplasm, causing 

 its death. The sap concentration theory of the disease also received support from its point of occur- 

 rence on the apple. Pit generally appears in the first instance on the upper half of the fruit and towards 

 the "eye" end (Figs. 28, 29). As the openings in the skin of the fruit are much more numerous towards 

 the "eye" end than on the basal portions, the larger number of openings at the "eye" end would 

 obviously allow more active transpiration, and consequently might render easier an undue concentra- 

 tion of the cell sap, leading to development of the Pit. 



