REPORT OF THE BOTANIST 245 



SESSIONAL PAPER No. 16 



not only unbroken but there is little or no alteration in colour. If cut into, however, 

 a pocket of dead and discoloured cells will be found lying immediately below. Ulti- 

 mately, this discolouration extends also to the surface layer of cells and the spots 

 become brown, the skin still remaining unbroken. They also often increase in size 

 and a number of them may coalesce to form one large affected area. 



It is found also that the superficial changes mentioned above are generally associ- 

 ated with deeper-seated ones in the flesh of the apple. On cutting such an apple, brown 

 spots may be seen scattered through it, chiefly in the more external region but some- 

 times extending almost to the core. Although seen in this way as isolated spots, if 

 carefully dissected out they will be found to be of the nature of strands rather than 

 of spots and follow the course of the vascular bundles or sap-tubes which they sur- 

 round. Either the superficial or the internal appearances mentioned may, however, 

 occur alone. In many cases, but not always, the dead masses of tissue have a bitter 

 taste which has led to the application of the term ' bitter pit.' 



Cause. 



No one has succeeded in finding any organism associated with this disease, and 

 from the work that has been done on it with negative results, it appears in the highest 

 degree probable that it is not of a parasitic nature. Hence no kind of spraying can 

 be. of any value. It appears to be caused by some inadequacy of the water or sap 

 supply at some stage in the development of the fruit, by which means certain of the 

 cells are deprived of their requirements in food and water. Whether the cells are 

 actually starved from want of food or whether the lack of water results in too great con- 

 centration of the substances in the cell sap is not clear, but the ultimate effect is the 

 death of the cells, which now form the discoloured areas described. As in so many 

 cases with these so-called physiological troubles it is difficult to make any recom- 

 mendations. The causal factors are on the one hand, rapid loss of water from the 

 fruit and on the other an inability to make good this loss with sufficient rapidity^ 

 Hence dry seasons or periods of drought may be expected to increase the trouble, while 

 much difference is to be found in different varieties in their degree of susceptibility, 

 on account of their varying powers of sap conduction, etc. There is no doubt that 

 this is one form of the so-called ' Baldwin Spot.' On the other hand recent investi- 

 gations point to a fungus (Cylindrosporium Pomi, Brooks), as being often the cause 

 of this disease, and in such cases a spraying given late in June or even early in July 

 has been found of value. The existence of two forms of disease, much alike in 

 appearance, but of totally different nature, one due to a fungus and the other to a 

 disturbance in the normal physiological conditions in the plant, will explain the con- 

 tradictory results of spraying experiments for the so-called ' Baldwin Spot.' 



A WESTERN APPLE DISEASE — APPLE TREE ANTHRACNOSE (GloeoSporilMl Malicorticis, 



Cordley). 



Specimens of this disease have been received from British Columbia, and a per- 

 sonal examination was also made of trees attacked on Vancouver Island. The disease 

 is known in the apple orchards of the Pacific Northwest of the United States, and has 

 also been recorded from Oregon and Washington. Casual untrained observers have 

 often confused frost injuries of the bark with this parasitic disease and, for this 

 reason, a careful description is necessary to prevent any errors of diagnosis, which may 

 naturally be followed by the loss of trees. Frost injuries may cause depressions and 

 discolourations of portions of the bark, and may give rise to cracks and cankers, and 

 thus closely resemble the Anthracnose, but the latter is readily distinguished by numer- 

 ous small ruptures in the sunken-in patches formed by the fruiting layers of the 



