Fig. 103.—Monocotyledonous Plant. larger than the others (see a in fig. 103). The trees belonging to this division are all natives of the tropics, and their softest and newest wood is in the centre, where fresh deposits are made every year inside the old wood; and hence, these trees are called endogens, which signifies, to increase from within. The wood of these trees has neither medullary rays nor concentric rings; and a section of it appears pierced with numerous holes (b), as may be seen by cutting off a slice of bamboo. The germination of a Monocotyledonous plant, with the cotyledon remaining in the ground, is shown at c.
The Dicotyledones and the Monocotyledones have all visible flowers, and are hence called Phanerogamæ; but the Acotyledones have no visible flowers, and they are hence called Cryp togamæ, which signifies that their flowers are hidden. The most remarkable of the Cryptogamous plants are the ferns, some of which become lofty trees; the wood of which is in curious wavy lines, as it appears to be formed by the footstalks of the decayed leaves growing together and becoming woody. The veins in the leaves or fronds of the ferns are forked.
Besides the great divisions already mentioned, the Dicotyledonous plants have been divided into the Dichlamydeæ, or those having both calyx and a corolla; and the Monochlamydeæ, or those having only a calyx; but there are so many exceptions, as to render this division of little value. The Monochlamydeæ are not subdivided, but the Dichlamydeæ are again divided into the Thalamifloræ, in which the petals and the stamens grow separately out of the thalamus or flat part of the receptacle, and generally from below the pistil; the Calycifloræ, in which the stamens and petals are either attached to the calyx, or to a lining of it formed by the dilated receptacle; and the Corollifloræ, in which the petals grow together, so as to form a cup for the pistil, and which have the stamens attached to the corolla, but quite distinct from the calyx. The Monocotyledones have also been re-divided into the Petaloid, or those with regular flowers, like the bulbous plants, and Orchidaceæ; and the Glumaceous plants, or those with scales or glumes instead of petals, as in the sedges and the grasses. The Acotyledones are divided into those with leaves, as the ferns; and those without leaves, as the mosses, lichens, and fungi.
I have only to add that each sub-class is divided into numerous orders, which are differently arranged by different botanists; the object being to place those nearest together which are most alike. As no one of these arrangements appears to be decidedly better than the others, I have adopted that given in Mr. Loudon’s Hortus Britannicus; marking, where, they occur, the new orders which have been formed, and the alterations in the old ones that have been made since that work was written.
CHAPTER I.
PHANEROGAMOUS PLANTS—DICOTYLEDONÆ—I. DICHLAMYDEÆ.
§ I.—THALAMIFLORÆ.
In all the plants contained in this chapter the receptacle is a fleshy substance called the thalamus, or disk, which is surrounded by the calyx, and out of which the carpels or seed-vessels, the stamens, and the petals, all grow separately from each other. Sixty-five orders are included in this division, but I shall only describe those which contain plants which have been introduced into Britain, except where the orders chance to contain plants well known in commerce.