192 AMEKICAN POMOLOGY. 



black, there is a precisely similar phenomenon; except 

 that the plates and filaments are very much larger, and 

 that each filament, when it falls off, leaves a ragged sear 

 behind it. In a single specimen of Black-knot noticed 

 August 6th, I discovered that the filaments not only cov- 

 ered the entire surface of the Black-knot itself, except 

 where a few of them had already fallen off, but that they 

 were thinly studded over the twig for an inch or two 

 above and below the swollen black part ; thus proving 

 tliat the fungus sometimes extends rather further than on 

 a cursory view it would appear to do. Towards the mid- 

 dle of August, the new Black-knot, having perfected its 

 seed, gradually dries up and becomes internally of a red- 

 dish-brown color. In other words, like so many other an- 

 nual plants, it dies shortly after it has perfected its seed, 

 just as a stalk of wheat or of corn dies shortly after the 

 grain is ripe. 



" 2d. During the months of June and July I collected 

 from time to time very numerous specimens of Black- 

 knot, some of which I out into to see what larvae they con- 

 tained, and Bom6 I preserved to see what perfect insects 

 could be bred from them. Besides seven specimens of 

 the common " Curculio," which many persons had previ- 

 ously bred from Black-knot, I bred for the first time there- 

 from no less than five distinct species of insects, none ol' 

 which can be considered as gall-makers, but not a single 

 true gall-m.iker ; and I can confirm Dr. Fitch's assertion, 

 that some specimens are wholly free from larvae of any 

 kind when cut into. 



" We will now take up in order the three different theo- 

 ries respecting the nature and origin of Black-knot, which. 



