136 STATE HORTICULTUKAL SOCIETY. 



penetrate to the living tissues, and set up the deadly fermentation of the car- 

 bonaceous food materials stored within the cells. The process is easily 

 observed without other aid than a pair of good eyes and a pocket-knife, though 

 the mischief-makers themselves require high magnifying to be seen. By 

 shaving off the outer bark in thin slices (a draw-shave is a good instrument to 

 us3) the tortuous holes made by the long, slender-bodied larvfe running, for 

 the most part, parallel with the outer surface, may be readily found in a 

 blighting Lombardy. From these holes may as readily be observed the 

 gradually spreading infection. The previously white and compact inner bark 

 becomes watery and fibrous, changing in color to a rusty brown. The boundary 

 line between the diseased and still healthy portions is sharp and easily deter- 

 mined, and may be observed, day by day, encroaching upon the healthy parts. 

 As is always the case, whatever has been, or is, thought to the contrary, the 

 blight progress is slow. It very gradually spreads from cell to cell, often 

 hardly enough to be noticeable, without careful measurements, during tAventy- 

 four hours. The broadly apparent effects, as the death of the leaves, may be 

 sudden enough, just as a mine explosion is sudden after weeks of laborious 

 drilling and cliarging. With abundant opportunity and extensive examination, 

 I have never found the roots of a Lombardy poplar in the least affected with 

 blight until after the disease had been communicated in the manner described, 

 by spreading from the parts above ground. The same is true of all kinds of 

 plants, woody or herbaceous, in which this blight has been observed. What a 

 commentary upon the periodically-revived idea that the heat of the soil is the 

 direct cause of blight! Bnt roots do suffer, and severely, too, through the 

 contagion from above, showing that their ordinary immunity is simply on ac- 

 count of their protection by the earth from an external, air-distributed foe. 



The aspen, tlie maples, the elms, the willows, the mountain ash, the lilac 

 (leaves), the butternut, some herbaceous plants (peony, lettuce, potato?), etc., 

 more or less, suffer in the same way, and on account of the same, or an indis- 

 tinguishable, voracious, little, but sufficiently potent, parasite. If it should be 

 demonstrated that the yellows of the peach is also due to the specifically 

 identical organism (which does not now seem to be the case), the process of 

 stamping out would be less hopeful. 



In this connection a pertinent query in regard^to the possible use to the pro- 

 ducing plant of the poisonous substances which many of them secrete forces 

 itself upon our minds. Why does the peach tree, especially in its wild state, 

 manufacture the deadly hydrocyanic acid and hold it within the starch and 

 chlorophyll cells? Why are the articles we call medicines stored so abundantly 

 in the bark of living trees and other plants? The fact that nearly all the alka- 

 loids, acids, essential oils, etc., thus stored away are destructive to bacteria-like 

 organisms is a curiously interesting coincidence if nothing more. By our pro- 

 cesses of cultivation and selection many plants lose in part these peculiar pro- 

 ducts as in the case of the garden parsnip. Are such cultivated and selected 

 plants therefore more exposed, more liable on this account to succumb to an 

 invisible but living and active enemy? Is the struggle for existence which we 

 find so universal in nature maintained in part by such means as these? It is 

 said that wolves will not touch the dead bodies of Mexican soldiers on account 

 of their saturation with the great amount of pepper these people use in their 

 food. Are many living plants similarly protected from equally voracious foes? 



Returning from this speculative digression I conclude by narrating an obser- 

 vation of the last season of practical interest to nurserymen. 



In May, 1881, I received through the mail a package of apple-tree root grafts 



