30 



BITTER PIT INVESTIGATION. 



was first observed on 21st December, in White Astrachans, fully ripe. The tree was about 25 

 years old, and the apple is very soft-fleshed, so that the disease is not always confined to 

 hard-fleshed varieties. 



The appearance of an affected apple is very characteristic. Externally the portion 

 affected has a waxy or glassy appearance, and this never extends over the entire apple. It usually 

 embraces the upper half or three-quarters, and the stem end is generally normal. (Figs. 66, 67.) 

 The transparent watery glassy appearance may occur over smaller or larger patches. When a 

 cross section of the apple is made, the glassiness is seen to extend even to the core (Fig. 68.), and 

 it is so firm and hard that it does not yield to the pressure of the ringer. The cells composing it 

 are all fully distended and turgid, so that they resist pressure. The glassy portion has a sweetish 

 insipid taste, and is deficient in the natural flavour of the sound portion. When analysed, it is 

 found to contain an excess of water, and a corresponding deficiency in acids and ash-constituents. 



The cause of the watery appearance is due to the intercellular spaces being filled with water 

 instead of air, as is usually the case. This may easily be shown by taking a microscopic section 

 just at the junction of the healthy and the glassy tissue. If water is added, the air in the ordinary- 

 tissue is replaced by water, and becomes transparent. The sound pulp is white, owing to the 

 air in the intercellular spaces. 



Glassy fruits are not only deficient in flavour, but they do not keep as well as the sound 

 ones off the same tree. On account of the excess of water, and the small acid and sugar content, 

 the internal diseased portions soon decay, and even the skin, which is remarkably thick over the 

 glassy portion, soon decays, and turns brown. 



It is generally observed that young trees are more liable to produce glassy fruit than when 

 they are older, although here, again, it is so dependent on a combination of conditions that no 

 absolute statement can be made. 



The three varieties most subject to it in Germany are given by Sorauer (85), as follows :— 

 Transparent de Zurich, White Astrachan, and Gloria Mundi. The fruit of the two former is 

 small or medium, while in the latter it is very large, one weighing 28 ounces having been grown in 

 South Australia. 



It has been found in the following varieties in Victoria :— 



Cornish Gilliflower. Mela Carlo (absolutely the White Astrachan. 



Early Almond. worst). Wine. 



Irish Peach. Prince of the Pippins. Winter Majetin. 



London Pippin. Bed Must— Cider Apple. Yarra Bank. 



Lord Suffield. Eoundway Magnum Bonum. 



Lord Wolseley. Stone Pippin. 



It is interesting to notice that Sorauer (85) attributes this glassy condition to some local 

 disturbance of the conducting tissue, while Pole Evans (31) considers it to be " undoubted evidence 

 of watery exudation under pressure." He says—" The cell sap fills the cells to overflowing, but, 

 instead of bursting them, quietly diffuses through their membranes or walls, and then accumulates 

 in the intercellular spaces." This certainly accounts for the intercellular spaces being filled with 

 a watery fluid, but it does not explain why, in " glassiness " of the apple, the water filling the cells 

 to overflowing does not burst their walls, but quietly diffuses through them, while in " Bitter Pit " 

 of the apple the same condition of affairs causes the bursting of the cells. The bursting of the cells 

 in the interior of the apple, due to too great internal pressure, is the most plausible theory yet put 

 forward to account for Bitter Pit, but it must be evident that there is a contradiction here 

 between the bursting of the cells in the one instance, and their turgid resistance to it in the other. 

 The contradictions will be reconciled when it is recognised that it is to the conducting tissue we 

 must look for the primary cause, and not to the cells themselves surrounding or adjoining it. 



