In clearing an uncultivated field we uproot a great number of herbaceous plants of different families; but those of the _Gramineæ_, or Grasses, invariably predominate. They are the trailing roots, or _rhizomes_, of certain species which have been included under the general denomination of Dog's-tooth. These tenacious and vigorous roots,--so wholesome in various maladies, so injurious to cultivation,--are, whatever certain botanists may say, far from tracing their origin in all cases to the _Triticum repens_ (couch-grass) and _Panicum dactylon_--those terrible enemies of the corn-field, which, once established in the soil, are with difficulty extirpated, and prove very injurious to the "golden crops." Nearly every grass which puts forth _rhizomes_ will furnish the _Dogs-tooth_. We may cite, for instance, several species of _Festuca_ (as _Festuca rubra_ and _Festuca pinnata_), or fescue grass; at least two kinds of meadow grass (_Poa compressa_ and _Poa pratensis_), a species of wild-oats (_Avena elatior_), to say nothing of the weeds _Arundo phragmites_ and _Arundo epigeios_. The long _rhizomes_ of these vivacious plants possess nearly the same properties, due to their saccharine principles. [Illustration: FIG. 22.--A Corn-field.] How shall we distinguish these plants from one another? Their leaves have almost exactly the same configuration; they are linear;[30] and their flowers are not apparent,--they do not attract the gaze of the passer-by. Yet they possess all the organs necessary for the reproduction of their species:--three stamens, each composed of an anther and a characteristic filament; on this anther, whose two lobes are arranged like the branches of an X, the pistil softly and tenderly balances itself on the summit of a frail thread, to which it is attached by the back. Remark, too, the two styles with feathery stigmata,[31] like the barbs of feathers. Nothing is wanting to constitute a complete flower. There is even a perianth, or calyx, represented by a couple of tiny membraneous scales, scientifically known as _glumellulæ_; then at the base of each spikelet, composed of one or two of these bright green lilliputian flowers, are two other and larger scales, called _glumellæ_: they represent an _involucre_.[32] It is almost unnecessary to add, that the free, unilocular ovary, or seed vessel, forms, as a result of its development, the seed, whose embryo adheres laterally to a farinaceous kernel, or _perisperm_. The union of one or more of these flowers composes a spikelet, and the union of the _spikelets_ constitutes the spike, which may be disposed on a simple or ramified axis. Such are, in general, the characters we must keep before us in the difficult study of the Gramineæ. Let us now see, more closely, the two plants which, according to the botanists, furnish the root of the Dog's-tooth. [Illustration: FIG. 23.--A River's Sandy Bank.]