412 REPORT OF STATE BOARD OF HORTICULTURE. 



Damage — The greatest damage is to the appearance of the fruit. The 

 bitter flavor is rarely so prominent as to be serious. 



Lamson* who has seen much of the trouble in Baldwins in New Hamp- 

 shire says that the disfigurement of the fruit is often so great as to render 

 an otherwise perfect apple a second. T. B. Wilson, a large apple grower of 

 Hall's Corner, New York, writes us that these spots " are a great annoyance 

 and cause quite a loss to the orchardists of Western New York." Craig, f 

 speaking of the conditions in Canada in 1896, states that while such apples 

 are not rendered wholly unfit for use their appearance and salability were 

 totally destroyed. 



Cause — Neither fungi nor bacteri are to be found in the earlier stages of 

 the spot formation nor is there a constant occurrence of any such organism 

 in the latter stages. It is therefore a non-parasitic disease. 



Wortmann's observations and experiments lead him to conclude that the 

 death of the cells in these spots is a result of the concentration of the sap 

 following the loss of water. This water may be lost by direct transpiration 

 in the case of the superficial cells, or in case of the deeper cells by excessive 

 conduction of the water to the transpiring surface layers. The acidity of 

 the concentrated sap is considered to be the direct cause of the injury, this 

 injury being followed by the browning through oxydization. 

 . Several factors may therefore enter into the problem of spot formation. 



1. The amount of rapidity of transpiration. This is dependent upon the 

 character of the epidermis, conditions of storage, etc. The fact is empha- 

 sized that gradual loss of sap is essential to the formation of typical spots. 

 Thus a specimen of a variety which is subject to spot will shrivel without 

 the appearance of spots if kept in a warm, dry room. Wortmann suggests 

 that in case of such rapid loss of water the acid of the concentrated sap has 

 insuflicient time to act. 



2. The kind and relative amount 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 spotting and nonspot- 

 ting varieties may not stand in a direct relation to their susceptibility to the 

 disease. 



3. The conductivity of the tissues of the' fruit. The original loss of 

 water must always occur at the surface. The death of these surface cells 

 may ultimately follow unless this loss is made good by the conduction to 

 them of water from the underlying" tissues. In some varieties this conduction 

 occurs more rapidly than in others. Wortmann found that in varieties sub- 

 ject to spot there was relatively slow water conduction. 



Bschokke considers this relative rate of water conduction to be the most 

 important factor in deciding the susceptibility of a given variety to the spot 

 disease. 



4. The specific resistance of the protoplasm of the cells to the injurious 

 action of the concentrated sap. This is probably greater in some varieties 



*N. H. Sta. Bui. 45, p. 4(> (1897). 



t Canada Exp. Farms Ilpt. 10, p. 171 (1896). 



