behind them the hemispherical plates, which alone had been hitherto noticed by the botanists. In another Epiphytous fungus, which grows commonly and abundantly in Illinois on the Red Cedar, but which differs from the Black-knot in being attached to the twig by a very short stalk or peduncle, and in being roundish and externally of a reddish-brown color instead of elongate and 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 scar behind it. In a single specimen of Black-knot noticed August 6th, I discovered that the filaments not only covered 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 that the fungus sometimes extends rather further than on a cursory view it would appear to do. Towards the middle of August, the new Black-knot, having perfected its seed, gradually dries up and becomes internally of a reddish-brown color. In other words, like so many other annual 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 cut into to see what larvæ they contained, and some I preserved to see what perfect insects could be bred from them. Besides seven specimens of the common "Curculio," which many persons had previously bred from Black-knot, I bred for the first time therefrom no less than five distinct species of insects, none of which can be considered as gall-makers, but not a single true gall-maker; and I can confirm Dr. Fitch's assertion, that some specimens are wholly free from larvæ of any kind when cut into. "We will now take up in order the three different theories respecting the nature and origin of Black-knot, which, as already stated, have been maintained by different writers. "1st. _That Black-knot is a mere disease like the cancer._--Dr. Fitch, who maintains this opinion, allows that the black granules found on the Black-knot are a true fungus, 'that the surface of these excrescences, when mature, is always covered with this plant,' and that 'this plant never grows, or at least has never been found, in any other situation.' (_Address N.Y. State Ag'l Soc._, 1860, p. 21.) * * *