Page:Popular Science Monthly Volume 28.djvu/87

Rh intended to attract the fertilizing bees. The young flower-heads are also inclosed in two papery wings or stipules, which effectually protect them from injury before they open. The petals are united into a very long tube, accessible only (as before noted) to the humble-bee; and in New Zealand, where our European humble-bee is unknown, it has been found necessary to import several nestfuls, in order to make the acclimatized clover set its seed for agricultural purposes. But the devices for the protection of the pod are here comparatively slight. Each pod contains, as a rule, only a single seed, and it is externally guarded simply by the wire-like calyx-teeth, which are long, thin, and awl-shaped, and fringed on either side by a row of thick-set hairs. The two lowest are longer than the others, apparently as a protection against crawling insects. After flowering, the petals remain upon the heads, turn brown, and inclose the ripening pod. These brown heads of overblown flowers have such a dead, withered appearance that they seem sufficiently to deceive all intending depredators. As a whole, the species seems to survive mainly because of its protected young flower-heads, its special attractions for fertilization, and its habit of inclosing the pods in the dry petal-tube. It should be noticed, however, that, though artificially propagated in meadows and pastures, it would not probably be a very successful plant if left entirely to its own devices. Man has intervened to give it his powerful aid by sowing its seed, and by fencing it off from cattle, so that it has now become, in spite of itself, one of our most abundant and ubiquitous clovers.

Next in order we may take a series of small, wild, purplish clovers, closely allied to this cultivated type, but more specially adapted for protection against animal foes. Of these the little knotted clover, which grows in our dry pastures and banks, is an excellent simple example. It is a small, tufted annual, often growing in very closely cropped, sheep-eaten crofts, and therefore with an acquired habit of creeping close to the ground, and spreading its foliage flat against the earth. Its calyx-teeth are short and almost prickly, and its little knotted heads grow so close in the angles of the leaves that even a sheep has hard work to bite them off with his nipping front teeth. The rough clover is another of these dwarf creepers, much like knotted clover in general appearance, but even more prostrate, and with its flower-heads still more closely wrapped up in the angles of the leaves, whose wings or stipules almost completely inclose them. The greatest difference, however, resides in the calyx, whose teeth here, after flowering, become broader and stiffer, curve backward, and give the whole plant a stringy, dry, innutritions look. This species or variety also grows mostly on sheep-bitten banks, and manages wonderfully to set its seed in spite of the manifold dangers to which it is exposed. Boccone's clover, confined in Britain to the Lizard Promontory in Cornwall, is a larger southern form of the same central type, closely