The sub-alpine glens which descend from our moors are the true localities of several of the rare Willows with broad leaves, and it is in such places they should be studied, rather than in Botanic Gardens, where their habits become materially altered by cultivation.
With the aid of the excellent works of DRS. HOOKER and TAYLOR, and the assistance of the microscope, the botanic student will be enabled to master the numerous species of Mosses and Jungermanniae, these minute vegetables, aptly denominated the watch-work of nature, seldom deviating into varieties, or appearing to pass into each other; but it will require glasses of higher magnifying powers, and the exercise of more patient attention, to arrive at a competent knowledge of the Algae and minute Fungi described in the elaborate publications of DR. GREVILLE; but, that this abstruse department of the science may be acquired even by persons whose time and attention are otherwise greatly occupied in professional pursuits, is evinced in the Flora of Berwick, a publication so highly creditable to one of our associates, DR. GEORGE JOHNSTON. Yet, notwithstanding these helps, the cryptogamic Botanist is still obliged to look to the continental writers for assistance, and must possess a part, at least, of the works of ACHARIUS, PERSOON, AGARDH, and DE CANDOLLE. Probably, the Botanicon Gallicum of DE CANDOLLE, in which a considerable proportion of the plants described by the before-named authors are comprised, will be found most useful, the climate of a large part of France differing not widely from our own. LINK, LYNGBY, and FRIES are the present guides among the most minute of Nature's vegetable productions, whose very genera are almost as unsettled as the sands on the sea shore.
SOWERBY's excellent delineations of the Lichens in the English Botany have materially facilitated the study of these intricate families, and their arrangement by ACHARIUS is probably as good a one, for mere practice, as could be adopted. Yet many individuals of these obscure tribes are to be found enumerated in his pages, not only as distinct species, but as belonging to more than one genus. This is owing in a great measure to the altered and degenerate state in which many appear when growing out of their natural localities, but more particularly to the slow mode of increase common to many of the crustaceous species. I have
