VARIOUS CAUSES ASSIGNED FOR BITTER PIT. 



63 



That Bitter Pit is not directly dependent on the amount of transpiration is shown by the 

 fact that a specimen of a variety subject to spot will shrivel without the appearance of spots if 

 kept in a warm dry room. Hence the gradual concentration of the cell-sap is essential to the 

 formation of typical spots. He suggests that, when there is very rapid loss of water, the acid of 

 the concentrated sap has insufficient time to act. 



2. The Quality and Relative Quantity of Substances in Solution in the Cell-sap. — The 



same degree of concentration of different solutions may not be equally injurious, 

 hence the actual per cent, of water lost in liable and non-liable varieties may 

 not stand in a direct relation to their susceptibility to the disease. 



3. The Conductivity of the Pulp Cells. — It is a well-known fact that there are spotting 



and non-spotting varieties, and Wortmann found, as the result of experiments 

 with peeled apples, that, in varieties subject to spot, there was relatively slow 

 water-conduction. Water is given off at the surface, and the death of these 

 surface cells may ultimately follow unless the loss is made good by water-conduction 

 from the underlying tissues. This conduction is more rapid in some varieties 

 than in others. 



4. The Specific Resistance of the Protoplasm of the Cells to the Injurious Action of the 



Concentrated /Sap.— The protoplasm of one variety is more susceptible or more 

 resistant to external influences than that of another variety, and so it is highly 

 probable that the protoplasm of the non-spotting sorts is more resistant towards 

 the action of the concentrated sap than the spotting. 



Wortmann concludes that the spotting of susceptible varieties cannot be entirely prevented, 

 but since trees which are improperly cared for produce fruit of less resistance towards unfavorable 

 influences of every sort, attention should be paid to general cultural conditions, and, above all, to 

 rational manuring. 



Zschokke (98), in 1897, continued the work of Wortmann, and critically examined it. He 

 pointed out that the structure of the epidermis, as given by Wortmann, did not bear out his 

 contention that the spotting sorts transpire more freely than the non-spotting, owing to the 

 epidermis of the former containing more openings and rents. Also, that the loss of water more 

 quickly and in greater quantity in the peeled non-spotting fruits did not point to more effective 

 protection by the epidermis, but merely proved that, in consequence of better and More regular 

 conduction of the flesh in the non-spotting sorts, more water was brought from the interior to the 

 transpiring surface. We ought not to lay too much stress on the structure of the epidermis, for 

 not only the number, but also the influence of the various openings on transpiration have to be 

 considered. 



He accepted Wortmann' s conclusion that the death of the cells is brought about by the 

 gradual concentration of the cell-sap, also that the spots arise in the neighbourhood of the vessels 

 and especially at the ends of the bundles. 



There are thus certain groups of cells favorably situated for the conduction of water towards 

 the surface, which lose more water than others, and, therefore, perish sooner owing to the 

 concentration of the sap. As a cause of spotting he adds another factor to those brought forward 

 by Wortmann, viz., the unequal rate of water conduction in the interior of the pulp. 



Massee (54), in 1906, received some diseased apples from Cape Colony, accompanied by 

 the following explanatory letter from the Cape of Good Hope Government Commercial Agency :— 

 " I have taken the liberty of forwarding to you one box containing apples of various kinds, which 

 have been grown in Cape Colony. You will notice that they are all disfigured with marks or 

 spots, and I am informed by the apple judges that these marks prevent the fruit being of any 

 commercial value. Would you kindly inspect them, and give me all the information that you 



