Bitter Pit in Aj^^ples. 1 1 



immature and unripe, while in other varieties, e.g., Jonathan, it 

 is unusual for it to become apparent till after a varying period 

 of storage. Very frequently no signs of the disease are visible 

 on the surface at all, but nests of diseased cells are present in 

 the interior of the fruit. (See Fig. 5.) These instances appear 

 to indicate that the-re is more than one period at which the 

 poison may gain access to the interior of the fruit. In cases 

 where the pitting occurs in the quite immature fruit the disease 

 is probably contracted when the fruit is quite young, shortly 

 after flowering. The epidermis from about the central part of 

 the surface of the young fruits belonging to a second crop of a 

 five-crown variety was examined, and it was found that the 

 stomata were open a week after the fall of the petals, and there 

 were 8 to 10 stomata. present in one square millimetre of apple 

 surface. (See Fig. 6.) TWo to three weeks later no stomata 

 were visible, their apertures being completely closed by growths 

 of new cells. Tlie function of the stomata is taken over by the 

 lenticels, which burst open soon after, and which rem-ain during 

 the life of the fruit, and it seems probable that poisonous 

 material from later sprayings enters through the lenticels, which 

 are almost invariably seen in the locality of the diseased areas 

 in those fruits in which the defect only becomes manifest after 

 storing. (See Fig. 7.) 



The poison which enters a stoma or lenticel in solution in 

 water is carried through the intercellular canals, where it 

 penetrates into the interior of one of the cells. All the cells in 

 the young fruit being meristematic are in process of extremely 

 rapid growth, and those cells surrounding that containing the 

 poison divide actively on all sides, and so leave the poison in 

 the interior of the fruit, without any apparent connection with 

 the exterior. All the cells in the flesh of the unripe fruit con- 

 tain innumerable starch grains, which are continujiUy being 

 hydrolysed into sugars by the action of a diastase enzyme wliich 

 has been shown to be present in large quantities in the unpollin- 

 ated receptacles of the apple, as set out in my previous paperi 

 on this subject. In the mature cells of the flesh of the ripe 

 apple, no starch grains are visible, having been all converted 



1 Journal of Department of Agriculture of Victoria, Dec, 1910. 



ujILIBR AR YJ- 



