young apple-trees accompanied by the usual deformation of the root. 

 Mr. Ira L. Bailey, President of the Carroll County Horticultural So- 

 ciety, North Illinois, likewise informed me that he had himself lost 

 three large apple-trees by the same universal "rotten-root." And fin- 

 ally I heard that Dr. Pennington, the extensive fruit-grower of 

 Whiteside Co., ISTorth Illinois, had sometimes noticed "woolly plant- 

 lice" on the limbs of his apple-trees, but not in any considerable num- 

 bers. Hence there is pretty satisfactory evidence that this insect 

 exists, though apparently in greatly reduced numbers, up to the most 

 northerly parts of the State. 



I found it to be a very general notion at Cobden, that the soil 

 there was full of this Root-louse — that it existed in earth that con- 

 tained no roots at all and in old rotten stumps — and that it wa< 

 abundant on the roots of almost all forest-trees, especially on those of 

 the Persimmon {Diospyros virginiana). No plant-louse, however, 

 can possibly live, except on the sap of some living and growing plant ; 

 and therefore, if any of these Root-lice are found in old dead stumps, 

 etc., they must, for purposes which will be afterwards explained, have 

 been carried there by the ants; as I have ascertained to be actually 

 the case with certain other species of the very same genus. That there 

 is a Plant-louse infesting the roots of the Persimmon in that neigh- 

 borhood, I fully believe; because, on digging down among the roots 

 of that tree, Mr, Riley and myself discovered the peculiar bluish- 

 white mould, which is characteristic of Root-lice, though we failed to 

 find the insect itself. But it is impossible that this can be the same 

 species as infests the Apple-tree, because the Persimmon and the Ap- 

 ple-tree, belong to widely distinct botanical families; and it is a rule 

 to which there is not one solitary exception, that, when a particular 

 species of Plant-lice infests more than one species of plants, those 

 species of plants always belong to the same botanical family, and 

 usually to the same botanical genus. For the same reason, if any 

 Root Plant-lice are found on Oak, Beech, Ash, Mulberry, Sassafras, 

 Tulip-tree (Poplar,) Cucumber-tree, Elm, Hickory, Walnut, Birch, 

 Poplar (Cottonwood, etc.,) Hackberry, Sumac, Dogwood, Grape-vine, 

 Sycamore (Plane-tree,) Hazel, Basswood, Maple, etc., they cannot 

 possibly belong to the same species as infests the Apple-tree, and, if 

 transferred to the roots of the Apple-tree, they would soon starve to 

 death and perish. On the other hand, it is highly probable, that 

 the very same species, that infests the roots of the Apple-tree* infests 

 also the roots of the Crab and the Thorn ; and it may possibly occur 

 on those of the Plum, the Cherrv and the Peach, and even on those 

 of the Blackberry and the Raspberry; for all these last named plants 



