TRANSACTIONS OF NORTHERN ILL. HORTICULTURAL SOCIETY. 335 



or breeding places for the fungi, and it spreads with great rapidity over 

 whole trees and forest, often taking on a peculiar virulent form, when it 

 appears to destroy perfectly healthy life as well as diseased. The punc- 

 tures of the leaf lice weaken the leaves, and also in that way make them 

 suitable prey for the mites, which, though delicate and highly organized 

 beings, breed with incredible rapidity, and are more evanescent even 

 than the April snow — swarming one hour, all gone probably the next — a 

 sudden change in the atmosphere destroying every individual, leaving 

 nothing of them behind, except their millions of eggs, which, if the 

 weather becomes again suited for them, at once hatch, and the army of 

 destruction is renewed. The mites, so far as I have observed, gnaw 

 down and feed upon the under cuticle of the leaves, so far as they go, en- 

 tirely destroying it, stomata and all. They also cover the entire under 

 surface of the leaf with a fine, close web, under which they feed ; this also 

 must greatly interfere with the functions of the leaves, by smothering them. 



So we see that it is not simply droughts, or severe winters after them, 

 that destroy our trees, though drought, or rather steady dry weather, is 

 the primal cause. A plant that has been preyed upon in its leaves, by 

 these enemies, has about the same chance of wintering safely, as a poor, 

 lousy calf, in the fall has. And what makes the trouble worse, is that we 

 cannot war against these things, to any successful extent ; all we can do 

 is to keep up vigorous vitality by cultivation. 



1 have penned this paper for two reasons : The one the paper ex- 

 plains ; the other, to call the attention of our scientific entomologists to 

 these vegetable-feeding mites, a department of their science that has not 

 had near the amount of practical consideration their noxious qualities 

 deserve. D. B. WIER. 



Lacon, III. 



Mr. McAfee to Mr. Wier — Do you regard thedroppingof the leaves 

 of the Delaware grape as the result of the work of the Phylloxera Vas- 

 tatrix ? 



Mr. Wier — To a great degree ; they and the acari weaken the vine. 

 The Concord, however, is almost exempt from the work of the Phyl- 

 loxera. 



Mr. Ellsworth said that in the early history of the Delaware vine, 

 its vigor was impaired, by propagation, for several generations of the vine, 

 from immature wood ; but that in later years, by propagating only from 

 well ripened wood, the vines had improved in hardiness. 



Dr. L. S. Pennington, from the Committee on Orchard Culture, 

 presented the following report : 



ORCHARD CULTURE. 



A finely developed tree is a thing of beauty, possessing, in its way, 

 the functions of assimilation and excretion — its winter's sleep and its sum- 

 mer's life — to make which more perfect is and should be our highest aim. 



