piliferous at the apex ; so close indeed is the resemblance in habit that M. D'Urville has remarked, "Je possede un echantillon de Gandichaud, double de taille, et voisin de notre L. clavatum" Such being the case, should L. clavatum be seen to vary in this respect, and especially if it is found to inhabit all intermediate latitudes between its northern habitats and Fuegia, we shall be obliged to conclude either that the plants are the same, or that L. magellanicum may be so sportive as to assume a form indistinguishable from the European plant. The former of these conclusions is generally admitted in such cases. The limits within which a species varies are acknowledged to be wider in one locality than in another, and two closely allied individuals may be modified almost infinitely without running into one another, as it is called; but, since the knowledge of specific difference is limited to the powers of observation, which are only attainable by the microscope, we are forced to acknowledge it possible that two totally different plants, inhabiting widely separated countries, may present to our senses a precisely similar appearance and remain undistinguishable; a conclusion which, if acted upon without caution, would lead to the subversion of all our confidence in what are universally confessed to be well established species.
The acute-leaved Lycopodia, which are not piliferous at the apex and otherwise closely allied to the L. magdlanicum, are L.fasligiatum, Br., and L. Pic/iincJiense, Hook. (Ic. PL t. 85), the latter certainly is, and probably the former also, a state of or identical with this ; both of them, though inhabiting a lower latitude, are only found at a great height. From Owyhee we have L, Jieterophyllum, Hook. (Ic. Fil. t. 113), in which the leaves are some of them simply acute as in the more southern form, but others piliferous and ciliated or erose at the margin, the former a very constant character in the L. clavatum, and the latter sufficiently obvious in some states only of that plant; in other respects this is not to be distinguished from the above or from a very common Chilian species, whose leaves have long acuminated points, and which seems identical with the L. dendromorp/ium, Kunze ; of this, however, I have only seen barren specimens, evidently passing into the L. arhtatum of the tropics, a very widely diffused and generally acknowledged variety of L. clavatum. Many states of X. clavatum are enumerated by Mr. Spring, in his account of the Brazilian Lycopodia, (vid. Regensburg Flora, 1838).
The last named author seems to have described from copious suites of specimens, and to have arrived, in most points, at the same conclusions with myself; thus, he has found it necessary to combine the L. alopecuroides, L. and L.longipes, Hook, and Grev., with L. inundation, L., to which must be added L. Mathewdi, Hook. (Ic. PI. t. 26), and perhaps L. contextual, Mart. (Fl. Bras. Crypt, vol. i. p. 38, t. 23, f. 1.), these species I had considered as merely forms of one, before Mr. Spring's paper was pointed out to me. The L. caroliuianiim, L., accompanies the last mentioned species throughout the temperate and warm parts of the American continent, and has also a very wide range through other countries, having been found in Tropical and South Africa, the East Indies, Madagascar, Tasmania, and New Zealand ; these two constitute part of a natural section allied to the Clavatum group in the spiked, more or less pedunculate fructifications, and ascending direction of the leaves on the prostrate stems, and to the Complanatum division in the tendency of the leaves of L. carolinianum to become distichous and decurrent, the other species of it are L. selaginoides, L. and L. pygmaum, Kaulf. A third group of species, which, like the former, have cylindrical spikes, contains — 1. the L. annotinum, L., a species spread over all temperate and Northern Europe, Asia, and especially America, where it is found as far south as the Alleghany and White Mountains. There are what appear barren specimens of this in Hook. Herb, from Dr. Wallich, under the MS. name of L. Heyneanum. In South America L. annotinum is represented by a more slender but very nearly allied plant, whose spikes are sometimes bifid and spuriously pedunculate; it is Hartweg's 1474 and 1479 from Colombia, where it has also been gathered by Professor Jameson. — 2. L. diaplianum, Sw., this is a Tristan d'Acunha species, very distinct in the form of the scales of the spikes and long piliferous apices of the leaves. — 3. L. sericeum, Mst., this is the L. scariosum, Hook. (Ic. PL t. 87, note), from Peru, one of the most beautiful species of the genus. I know of no others very closely allied to these, they rank near the Clavatum group, from which indeed they only differ in the truly sessile spikes, and also approach that containing L. complanatum, through L. alpinum, whose spikes are sessile.
The L. ceruuum, L., may be considered as the type of another natural section, it is perhaps the most abundant
