48 



the fact that they have not the first conect idea upon the subject on which 

 they are writing. 



Tiie truth is, these three maladies, about one and another of which so 

 mucli has been said, are all one thing — diffoiing merely as cause and effect. 

 If there were no lice on hops there would be no honey dew and no black 

 blight. I am aware the hop growers will be much surprised at this state- 

 ment, and will scarcely credit it, they have been so accustomed to regard 

 these things as distinct from and in no wise connected with each other — 

 deeming the honey dew to be a fluid which has exuded from the leaves in 

 consequence of some disease therein, and the black blight to be, asalready 

 stated, a kind of fungus growing from the leaves, whilst the plant lice, 

 occurring only on the opposite or under side of the leaves, appear to bo 

 wholly separated from these substances upon their upper surface. But I 

 am perfectly assured of the correctness of what I say, and can produce 

 specimens which will demonstrate that I am correct. I regret tliat this 

 subject did not occur to my mind last summer, or I would have had such 

 specimens for exhibition here at this time. Upon the first opportunitj', I 

 will procure and place in the Museum of our Society, specimen of leaves 

 showing this honey dew upon them, and others showing the black bligiit; 

 and by the side of these leaves I will place white paste-board cards having 

 the same honey dew and the same black blight upon them — thus demon- 

 strating that these substances do not exude and grow from the leaves unless 

 they also exude and grow from the paste-board cards. 



I will now briefly explain how these two substances come upon the 

 leaves. 



Each Aphis has two little horns projecting from the hind part of its back, 

 which horns are termed the honey lubes. From these tubes the fluid called 

 honey dew is ejected, in the form of minute drops, like particles of dew, 

 which, falling upon the leaves beneath tliem, the upper surface of the leaves 

 becomes coated over with this fluid, more or less coplou.->ly as the Aphides 

 producing it are more or less numerous. And now, th s deposit of honey 

 dew being exposed to the action of the atmosphere and alternatelj' moist- 

 ened by the dews at night and dried by the sun by day, is gradually decom- 

 posed, changing from a clear, shining, transparent fluid, to an opake, black 

 substance resembling soot, and it is then the black blight. In this simple 

 manner do we account for and explain these phenomena — these three impor- . 

 tant diseases of the hop, about which so much has been said and such eru- 

 dition has been displayed by some of the writers in our newspapers. 



These same phenomena, called honey dew and black blight, are not pecu- 

 liar to the hop, but occur on other kinds of vegetation when infested by 

 plant-lice; and an abundance of authority will substantiate my statement 

 that this honey dew is caused by these insects. But I find no allusion to 

 the black blight in any author, and what I state of that is the result of my 

 own observations. It is proper, therefore, that 1 here adduce some of the 

 evidence which I have, upon this particular point. 



It is over twenty years ago that I first noticed this blackness as being 

 occasioned by plant-lice. Among several willow trees by the side of a 

 stream near my residence, there was one so thronged with the willow aphis 



