Fruit Brevities. 433 



trees from which the knots were not removed, tend to develop 

 still more knots. Mr. Smith's paper brought out a discussion 

 from Mr. Yates, the larger part of which I am glad to quote 

 (California Fruit Grower, Feb. 9, 1895, 111), particularly as his 

 conclusions are essentially like those of Sorauer: 



*' In common with many other horticulturists, Mr. Smith as- 

 sumes the root tumor to be a disease, which in the strictest sense 

 of the word it is not, as the tumors when first foimed are com- 

 posed of healthy cellular tissue; disease being afterwards super- 

 induced by the abnormal condition of the enlargements interfer- 

 ing with the proper functions of the sap in regard to circulation. 



" My first investigations of tumor were made with the idea that 

 possibly such curious growths resulted from an inherited cause, 

 or were perhaps the work of minute fungi and therefore conta- 

 gious; so I budded, grafted and inoculated unaffected from 

 affected trees, but all to no purpose; the tumors refused to be 

 reproduced. , 



" But while investigating along this line, I noticed that 

 wherever the free circulation of sap under certain conditions had 

 been checked or imj)eded, it was no uncommon thing to see some 

 of these tumors commence to form, and several years' observation 

 has but served to convince me that they are primarily caused, 

 either by impeded circulation of sap and consequent disorgani- 

 zation of the sap vessels and surrounding tissues, or by a lack 

 of equality in the absorption of moisture by the roots and its 

 transpiration by the leaves and branches. 



" In the first instance, the sap being forced out of its regular 

 channels and unable under these changed conditions to perform 

 its proper functions, commences to throw out callus formations, 

 which enlarge very rapidly owing to the amount of sap forced 

 into them through what is generally known as the core of the 

 knot. This mass of callused matter thus irregularly formed 

 becomes after a time diseased, and it is at this stage that the 

 fungus growths have been found which have led many investi- 

 gators into the error of supposing these tumors to be the result 

 of fungi. The causes of this impeded circulation are many; 



28 



