Scientific writers have examined no less than a thousand different species of Agarics, or those fungi belonging to the class of mushrooms, and probably there are many more than have yet been enumerated. Some few only of these plants are edible; a large proportion are highly poisonous to man, while the character of many more have never yet been ascertained. It is particularly remarkable that those which are found wholesome in one country often become very dangerous in a different soil; in England, for instance, only three kinds are eaten, the _Agaricus campestris_, or common mushroom, the _A. pratensis_, or fairy- ring mushroom, and the _A. Georgii_; but in southern Europe many more are used as food, and among these a number of the same species which in Great Britain have proved very dangerous. In Kamschatka again, the _Agaricus muscarius_, considered a deadly poison in England, is found quite harmless, and is regularly used as food. The following directions have been given in avoiding poisonous mushrooms; all those possessing either of the characteristics mentioned being dangerous: 1. Such as have a cap very thin compared with the gills. 2. Such as have the stalk growing from one side of the cap. 3. Those in which the gills are of equal length. 4. Such as have a milky juice. 5. Those that readily produce a dark, watery liquid. 6. All those that have a thin, web-like substance wound about the superior portion, or collar of the stalk. As yet little has been printed regarding our American Agarics, while those of Europe have been very closely studied by many scientific men, who have published the result of their investigations. The following is a list of those mentioned by Mr. Knapp in the volume before the reader: _agaricus fimiputris_; _a. æruginosus_; _a. odorus_; _a. fragrans_; _a. varius_; _a. oreades_; _a. georgii_ or _arvensis_; _a. surrectus_; _a. caseus_, (or _infundibuliformis_;) _a. campestrus_; _a. pratensis_; _a. muscarius_; _hydnum floriforme_, or _h. compactum_; _helvella mitra_, (or _h. crispa_;) _lycoperdon cinereum_, or _didynium cinereum_; _l. fornicatum_, or _geaster fornicatus_; _l. stellatum_, or _g. hygrometicus_; _morchella esculenta_; _phallus impudicus_; _clavaria hypoxylon_. These Agarics are all found in the United States, with the exception of two species, _a. varius_, and _a. surrectus_, considered as yet unrecognized. _A. georgii_, is regarded as a variety only of _a. arvensis_. The esculent morell, _morchella esculenta_, noted by Mr. Knapp as very rare in his own neighborhood, is widely diffused throughout the United States. In some parts of the state of New York it is prized as a delicacy for the table, and in the old orchards of Westchester county, for instance, is by no means uncommon. NOTE Q. THE MARTEN, (_Mustela Martes_,) p. 95.