THE CONTROL OF BITTER PIT. 61 



cells. This burden was formerly shared by the vascular bundles, but now the distended pulp-cells, 

 like so many little balloons (filled with sap instead of gas), have to prevent the structure from collapsing. 



That it does collapse here and there, producing the brown flecks in the flesh, is not to be wondered 

 at, and the problem of Bitter Pit, like that of modem civilization, is to strengthen the constitution 

 against the forces which tend to weaken it. 



I submitted a summary, giving the results of my work on the cause of Bitter Pit, to Professor 

 Ganong, of America, the distinguished author of The Living Plant. He gave it his careful attention, 

 and replied : "Your conclusions certainly look to me very reasonable and probable, and, as far as I 

 can tell, seem wholly consistent with our knowledge of osmotic and sap-pressure phenomena. 1 

 would have to give, however, a great deal more study to the subject than is practicable to make any 

 suggestions, after the exhaustive work which you have done upon the subject." 



The various factors which increase or diminish Bitter Pit react upon the vascular system of the 

 apple, which has been fully described in previous Reports. The Pit originates beneath the skin, 

 where the symmetrically formed network of vessels surrounding the outer layer of pulp-cells and form- 

 ing the boundary between skin and pulp is situated. Wherever Bitter Pit occurs this network is 

 ruptured (as shown in Report I., Fig. 90), owing to the pressure exerted by the too-rapid growth. 

 The pulp-cells, at first enclosed by the ruptured meshes of the net, arc likewise burst, and death 

 ensues. It is this wonderful network of vessels beneath the skin, forming distributing channels to 

 regulate the pressure of the sap, that explains the occurrence of Pit in spots or patches. Hence the 

 rupture of the. vascular network here and there, and of the adjoining pulp-cells in localized spots, due to 

 over-pressure of the sap, is the exciting cause of Bitter Pit, and the oxidizing enzyme in the presence of 

 tannin, causes the group of burst cells to become brown. 



THE CONTROL OF BITTER PIT. 



The control of Bitter Pit in the fruit, both while growing on the tree and in oversea shipments, 

 was the final object of this investigation, and a study of the cause was a necessary preliminary. 



It has been proved experimentally that when fruit is picked on the green side or just when it is 

 beginning to reach the ripening stage, and kept in cold storage at a temperature of 30-32 degrees 

 Fahr., the development of Bitter Pit is retarded and the ripening process arrested. 



From the very nature of the disease it is hardly possible to prevent it altogether while the fruit 

 is still growing on the tree, but it has been found practicable to reduce it to such an extent that the 

 loss is comparatively trifling. 



The results of experiments in different States enable us to draw the conclusion that light pruning 

 is associated with a small amount of Pit, and severe pruning with a large amount. 



A special pruning experiment, extending over five years, with Cleopatra trees which were nine 

 years old to start with, and had been so badly affected with Pit that the orchardist had cut most of 

 them down, shows the effect of pruning very decidedly. The leader and lightly pruned trees had the 

 largest crops with from 4 to 6 per cent, pitted, while the severely pruned trees had 22 per cent, pitted. 



Where irrigation is practised, a proper use of the water will help to reduce Pit. An experiment was 

 conducted with a susceptible variety at the susceptible age of five years. Where the trees were lightly 

 watered throughout the season there was 14 per cent, of Pit, while in trees with a medium supply of 

 water at first, but a heavy watering towards the end of the growing period, Pit was much worse. The 

 heavily watered trees showed over three times the amount of Pit, or 49 per cent. 



The application of sulphate of iron, in several instances, gave very promising results, and it is 

 worthy of being tried on a large sc'ale, as well as for a sufficient number of seasons. 



