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, _F_, _H_), minute floating plants without any differentiation of the plant body into stem and leaves. They are globular or discoid masses of cells, most of them having roots; but one genus (_Wolffia_) has no roots nor any trace of fibro-vascular bundles. The flowers are reduced to a single stamen or carpel (Figs. _E_, _G_, _H_). The cat-tail (_Typha_) and bur-reed (_Sparganium_) (Fig. 86, _I_, _L_) are common representatives of the family _Typhaceae_, and the pond-weeds (_Naias_ and _Potomogeton_) are common examples of the family _Naiadeae_. These are aquatic plants, completely submerged (_Naias_), or sometimes partially floating (_Potomogeton_). The latter genus includes a number of species with leaves varying from linear (very narrow and pointed) to broadly oval, and are everywhere common in slow streams. The largest members of the group are the screw-pines (_Pandaneae_) and the palms (_Palmae_). These are represented in the United States by only a few species of the latter family, confined to the southern and southwestern portions. The palmettoes (_Sabal_ and _Chamaerops_) are the best known. Both the palms and screw-pines are often cultivated for ornament, and as is well known, in the warmer parts of the world the palms are among the most valuable of all plants. The date palm (_Phoenix dactylifera_) and the cocoanut (_Cocos nucifera_) are the best known. The apparently compound ("pinnate" or feather-shaped) leaves of many palms are not strictly compound; that is, they do not arise from the branching of an originally single leaf, but are really broad, undivided leaves, which are closely folded like a fan in the bud, and tear apart along the folds as the leaf opens. Although these plants reach such a great size, an examination of the stem shows that it is built on much the same plan as that of the other monocotyledons; that is, the stem is composed of a mass of soft, ground tissue through which run many small isolated, fibro-vascular bundles. A good idea of this structure may be had by cutting across a corn-stalk, which is built on precisely the same pattern. ORDER IV.--_Glumaceae_. The plants of this order resemble each other closely in their habit, all having long, narrow leaves with sheathing bases that surround the slender, distinctly jointed stem which frequently has a hard, polished surface. The flowers are inconspicuous, borne usually in close spikes, and destitute of a perigone or having thi
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