442 BOARD OF AGRICULTURE. 



in either of these cases, the fungus which covers and dis- 

 figures the diseased parts of the trees a secondary feature of 

 the disease. M}'' ohservations of later years, with grape- 

 vines and currants in particuhir, have tended to strengthen 

 in my mind that view in regard to many of our troubles 

 with parasitic growth and diseases of plants. I have re- 

 peatedly noticed that plants suffered seriously from mildew 

 and blight upon unfertilized and exhausted lands, when upon 

 adjoining fertilized plats no sign could be noticed. On the 

 other hand, the healthy condition of the roots, even to the 

 last stage of the disease, and also the gradual disappearance 

 of the green color, indicating insufficient production of 

 chlorophyll, which causes the gradual change from a healthy 

 appearance to a sickly one, beginning with the outer ter- 

 mination of the branches, which is the most active part for 

 the formation of new vegetable matter, seemed to point 

 towards a localized trouble, — a possible interference with 

 the normal cellular functions, — an alteration of the osmotic 

 action of the cellular tissue, and thus subsequent death of 

 its affected part. This view of the case found support in 

 the well-known observations of Messrs. Nobbe, Schroeder, 

 and Erdmann (Chemnitz, 1871), regarding the action of 

 sulphate of potassa and chloride of potassium on the grow- 

 ing of rye and of buckwheat. Sulphate of potassa had 

 caused first a premature yellow color of the entire plant, 

 which terminated with its gradual failing ; whilst the chlo- 

 lide of potassium (muriate of potash) had caused a vigorous 

 growth, a rich, dark-green colored foliage, and a successful 

 ppoduction of grains. 



An examination of the cellular tissue of the diseased plants 

 had shown an excessive accumulation of starch in the cel- 

 lular tissue, indicating thereby a retention of that constitu- 

 ent, and but little chlorophyll was noticed. On the strength 

 of these results I began, in 1878, to treat slightly affected 

 trees with a phosphatic fertilizer in the usual proportion, 

 adding at the same time from three to four pounds of chlo- 

 ride of potassium (muriate of potash) for every tree, and 

 the diseased branches were cut back once or twice to the 

 healthy wood. Soon after, the new growth of the branches 

 regained its green color. The details of this work were 



