66 BOARD OF AGRICULTURE. 



vorable in both conditions, and I have been led to the conclu- 

 sion that there was some cause at work other than the mere 

 presence or absence of sod. I am inclined to think that the 

 pear blight is a constitutional disease, and the line I am 

 working upon at present is upon the basis of nutrition. I 

 am aware that certain experiments have been made tending 

 to show that the pear blight is developed directly l)y inocu- 

 lation ; by the direct operation of pathogenic bacteria. I 

 have examined hundreds of pear trees, and I have not yet 

 been able to find, with one exception, — and that we could not 

 operate upon, — a pear tree which would so satisfy the true 

 condition of normal health that we would be willing to sub- 

 mit it to the inoculation system ; but some experiments 

 which have been performed abroad seem to indicate that the 

 disease is an infectious one and can be propagated by inoc- 

 ulation from one tree to another. I am inclined to believe, 

 however, in the absence of testimony to the contrary, that 

 the subjects were not in proper condition for inoculation. 



Mr. Ware. My observation is that the pear blight comes 

 upon one limb in one year, and perhaps another year upon 

 another limb, but the whole tree is not affected at the same 

 time. That would seem to indicate that the whole tree is 

 not constitutionally affected or diseased, but the disease is 

 local. 



Prof Penhallow. That is where a mistake is commonly 

 made. The trouble is th;»t a sufficient number of experi- 

 ments are not undertaken for the dctermmation of the dis- 

 ease when it appears ; and as a matter of fact, I feel very 

 well convinced that the disease has existed in the tree for 

 some time previous to what we generally consider the ap- 

 pearance of the disease as manifested in the l)lackcned limb. 

 In fact, the blackened limb is evidence of the last stage of 

 development. It is proof that the limb has actually died 

 from the disease, and the black color is evidence of decom- 

 position, not that the disease first attacks the tree at that 

 time. By tracing back the blight in the limb, in the trunk, 

 in its various forms, I am well satisfied that it appears often 

 in a more localized form than where it involves the entire 

 branch. For instance, black spots appear frequently upon 

 the trunks of small pear trees, not more than half an inch 



