The lycopodia, or club-moss tribe, are also very widely distributed among the coal-measures, and attained in the earlier ages of the earth’s history an equally gigantic size with the tree-ferns. At the present day, they are all weak, prostrate plants, of from two to three feet in length, and, following the same laws as the mosses and ferns, they are most abundant in hot, humid situations within the tropics, and especially in the smaller islands. As respects their botanical affinities, the lycopodiums are intermediate between ferns and coniferæ on the one hand, and ferns and mosses on the other; related to the first of those families in the abundance of annular ducts contained in their axis, and to the second in the whole aspect and outline of the stem of the larger kinds. Indeed, so great is the resemblance between lycopodia and certain coniferæ, that there is no other external character, except size, by which they can be distinguished; and, according to Professor Lindley, it is, at least, as probable that some of those specimens detected in the ancient flora of the world, which have been considered gigantic club-mosses, are really and truly pines, as that they are flowerless plants. Another family of fossil plants abundant in the coal formation are the calamites, so named from their jointed reed-like structure. They attained to the size of trees, trunks upward of a foot in diameter being often met with, but still of such a soft succulent texture as to maintain the character of being, if reeds, easily shaken by the winds. These, and various specimens of the palm tribe, are to be found in every coal-field, and often in such vast masses as to show that they constituted no inconsiderable proportion of the flora of the period. Palms now only flourish within the regions of the tropics, where, from their various properties, as well as great productiveness as fruit-bearers, they constitute the chief source of dependence to the inhabitants for all their supplies of the necessaries, luxuries, and medicines of life. A single spathe of the date contains about 12,000 male flowers: another species has been computed to have 207,000 in a spathe, or 600,000 upon a single individual. The spathe constitutes the raceme or flower-stem of the tree, and on a single raceme of a Seje palm, Humboldt estimated the flowers at forty-four thousand, and the fruits at eight thousand. When these magnificent productions of nature covered the plains and marshes of our northern climes, there were no roaming tribes to gather their fruits, inhale their fragrance, or bask in their shades. And yet they were not formed in vain. Buried in the rocks, their collected remains now yield a product as useful and valuable to the human family—as contributive to intellectual improvement, as they would have been to mere animal enjoyment.