106 Ex])eriment Station Report. 



ject iu the present report, although little that is new and of 

 general interest can be added beyond the fact that the 

 restored trees are healthy and bearing, and that new trees 

 planted in the places where diseased trees have been re- 

 moved,* have been bearing healthy fruit during the past 

 season. The subsequent observations were made on peach 

 trees planted in 1870 in the orchard of the College, and not 

 on the young trees upon the experimental plats of the 

 Station. 



The experiments began in the fall of 1877, when my at- 

 tention was first called to the appearance of the disease in 

 the College orchard, on the top of a knoll of light soil. 

 The general appearance of the trees at the first stage of the 

 disease suggested to my mind the idea that an abnormal con- 

 dition of the soil might be the first cause of its development. 

 This circumstance could be due either to a more or less gen- 

 eral exhaustion, or to the absence of only one or the other 

 essential elements of plant-food ; or finally, to the presence 

 of some injurious substances which might have accumulated 

 in the soil from some cause or other in the course of time. 



The gradual disappearance of the green color (chlorophyl) 

 in the leaves, beginiiing at the outer termination of the young 

 branches, — which are the most active parts of the plants for 

 the formation of new vegetable matter, — seemed to point 

 towards a local interference with the normal cellular func- 

 tions, a natural consequence of an abnormal sap. I felt 

 inclined to consider the fnngus which, in its gradual develop- 

 ment, disfigures the diseased parts of the tree, a secondary 

 cause of their ultimate condition. My observations of later 

 years with grape-vines and currants in particular, have 

 tended to confirm in my mind the view that our troubles 

 with parasitic growth on plants are in many instances due to 

 an abnormal condition of the soil, rather than to a particular 

 condition of the atmosphere. I have repeatedly noticed that 

 plants sufi'ered seriously from mildew and blight upon un- 

 fertilized and exhausted lands, when upon adjoining fer- 

 tilized plats neither could be noticed. Diseases of plants 

 are known to originate from internal and external causes, 



* See Prof. Maynard's appended Report. 



