190 AMBEICAN POMOLOGY. 



they apply it, I subjoin a full account of all that is at 

 present known on this subject, and of the different theo- 

 ries respecting it entertained by different writers. 



" Three radically different theories have been broached 

 as to the nature and origin of Black-knot : 1st, that it is 

 a mere disease of the tree, like the cancer or the gout in 

 the human race, which is the view maintained by Dr. 

 Fitch, the State Entomologist of New York ; 2d, that it 

 is what naturalists term a " gall," produced by some un- 

 known insect depositing its eggs in the twig — just as the 

 well-known "oak-apples" are produced by a Gall-fly, 

 (Ct/nyps), depositing its egg in the bud of the oak — 

 which is the opinion that I myself formerly held and main- 

 tained, before I had fully examined into the subject ; {I^o- 

 ceedinga Ent. Soc, Phil., Til, p.p. 61S-618 ;) and 3d, that 

 it is what botanists term an epiphytous fungus, growing 

 on the tree as a mushroom or toad-stool grows on the 

 ground, which is the opinion of the botanist Schweinitz, 

 and which has recently been re-asserted by Mr. Glover, 

 the Entomologist of the Bureau of Agriculture at Wash- 

 ington, {AgH Hep., 1863, p. 572.) This last is the opinion 

 which, upon full inquiry, I have now adopted. 



" Before discussing these theories, the facts arrived at 

 by myself in the summer of 1863, must first be briefly 

 noticed. It should be premised that the old, dry Blaok- 

 knot remains on the tree for many years, and that the 

 place to look for the new Black-knot is on such trees as 

 liave been already attacked and are loaded with old Black- 

 knot, without being as yet completely killed by it. 



" 1st. By the middle of June the new Black-knot is 

 pretty well developed, and may then be readily distin- 



