78 



BITTER PIT TN VESTIGA TI ( >X. 



Here, again, each individual apple of the lighter crop has received an extra supply of nutriment, and 

 the over-gorging of the pulp-cells will tend to prevent the network being equally formed at the 

 periphery, where the most rapid and greatest amount of growth is taking place. It has sometimes 

 been pointed out to me that it is not always the largest apples on a tree which are affected, for in 

 a cluster the small apples may be pitted and the larger ones escape. But it must be remembered 

 that, while the general rule holds, there may be modifying factors to account for the exception. It 

 is recognised by every orchardist that in a cluster of fruit it is the topmost or central one which shows 

 the greatest amount of growth, yet in Fig. 20 I have shown a cluster of pears where the topmost 

 one is the smallest. This exceptional occurrence could easily be explained, but an isolated instance 

 does not interfere with the general principle. 



Again, it is noticed by the observant orchardist that the more quickly-maturing apples on 

 the tree are most liable to pit. In picking apples, especially for the oversea market, it is customary 

 to go round the tree and select those which are most developed and of uniform size, leaving the 

 others to mature. After a few weeks, under ordinary conditions, it is found that the smaller ones 

 have grown bigger, and it is known by experience, as well as the result of the sales, that these are 

 not so liable to develop pit. Further, it is sometimes observed that an older tree, especially when 

 growing on a headland and left uncultivated, may be comparatively free from pit, while adjoining 

 trees well cultivated and cared for may develop it. But it is evident here, from the conditions of 

 the case, that there is not that stimulating and vigorous growth which would produce excessive 

 transpiration and the undue development of the fruit. 



Finally, reduced transpiration may be dependent on the nature of the fruit, and circumstances 

 which would escape the observation of the ordinary orchardist. If a young Cleopatra apple, for 

 instance, is carefully examined, it will be found that it is enveloped by a dense covering of hairs. 

 This woolly covering protects the surface from the currents of air which sweep over it, and tend to 

 dry it up. The compact hairy felt renders the air stagnant over the pores, and thus reduces the amount 

 o£ transpiration. This principle is also well illustrated in some grasses, which develop a dense 

 covering of hairs when growing in exposed situations, as on mountain tops, while in sheltered 

 situations, as in valleys, the same grass may be destitute of hairs. 



No doubt this hairy covering has something to do with the comparative freedom from pit 

 of the quince, which is covered with hairs even to maturity, while the apple loses its hairs when it 

 has reached the size of a walnut. Young Cleopatra apples were obtained from Burnley Gardens 

 on 14th November of the size of hazel nuts and walnuts. On close examination the hairs were 

 found to have fallen away, except around the base of the stalk and just at the " eye." After the 

 fruit has set and the petals have just fallen, it is covered with a dense mass of hairs. 



To regulate and control the transpiration is one of the most important factors in preventing 

 the development of Bitter Pit. To this end the addition of humus to the soil by green manuring, 

 light pruning so as not to reduce the transpiring surface too much, cultivation by keeping the soil 

 at a more uniform temperature by night as well as by day, drainage to keep the temperature more 

 even, liming to improve the physical condition of the soil, and by applying water at the right time 

 and in proper proportions by means of irrigation, will all tend to make the growth of the fruit regular 

 and even. 



The experiments now being carried out, as detailed in Section XXII., will deal with all these 

 factors, and show, as far as possible, in the limited period of the investigation how far, individually 

 or collectively, they have a controlling influence upon the development of Bitter Pit. 



REMEDIAL MEASURES. 



It is rather premature to suggest remedial measures until the results of experiments now 

 being conducted are known, but the practical conclusions drawn from the experience of German 

 orchardists may be given. These were obtained from 107 replies to questions, and they were 



