It should be added, however, that if the rain continue for several days, the pimpernel will lose its sensibility, and cease to act as a natural weather-glass.
And here we may observe, that singular as is the habit of the flowers anticipating rain by folding their petals within their calices, the way which the Siberian sow-thistle has with it is still more curious. This plant, during that clear weather which most flowers affect, keeps entirely shut; but as soon as a thick mist overspreads the earth, or a cloud obscures the bright face of heaven, it begins to open its light blue corolla.
Everybody knows, or should know, that when the robin looks sad and drooping, and ceases to greet you with his wonted blithesome strain, "foul weather" is at hand. Many animals, by their peculiar habits, afford equally certain indications of approaching atmospheric changes.
This does not seem strange to us; we account for it by the instinct which every animal possesses, in a larger or smaller degree. But the same anticipatory faculty is possessed by several plants; they feel the increasing moisture of the air long before it can be detected by ourselves. Thus, when a storm is at hand, some species of anemones fold up their blossoms; the fragrant flowers of the wild pink convolvulus wind themselves together; the awns of the wild oat, and the sweet-scented meadow-grass, stand in an erect position, and the clover leaves are drawn closely up.
Naturalists, says Pratt, are unable to discover why some plants should be affected by moisture and others not; but the regular changes of these natural barometers seem a providential arrangement to supply certain wants of the flowers in which they occur. We may draw this inference from the different positions of several flowers according to their circumstances. Thus the poppy, when in bud, hangs down on its stem, and preserves its petals from rain and wind; but as soon as it is fully developed, and has acquired strength, and the sun's rays are necessary to perfect its colours, it expands to the full light of day. The violet, again, while its seed is forming, shades the capsule by its purple corolla; but as soon as the seeds are ripe, and they are required to spring to some distance from their capsules, the flower immediately rises up with the cup for its support, and flings abroad its offering on the earth's maternal bosom. Adaptations of this kind are frequent and striking in the vegetable kingdom, and surely one is justified in regarding them as the work of an all-powerful and all-wise Creative Mind. Look, for instance, at the orchis: it grows on the ground in Europe, and is consequently provided with roots formed of large lobes; but when it festoons the pillar of the virgin forests of the New World, its roots are formed of a number of fibres, so that they may penetrate the bark of the tree.
But to return to our pimpernel. It was at one time called Centunculus, from cento, a covering, because it spread in such abundance over the cultivated fields. Its botanical name was afterwards changed to Anagallis arvensis. Anagallis signifies "to laugh," and there existed an old belief that a decoction of the pimpernel acted as a remedy against melancholy, and a provocative of mirth.
The seeds of this plant are very numerous. They are enclosed in small capsules, and eaten by the birds.
There is only one other British species of pimpernel, the Anagallis linetta, or bog pimpernel, which it would be unpardonable if the botanist omitted to notice, so delicately beautiful are its pale-rose blossoms and tiny clusters of leaves. As its name indicates, it is found only in marshy localities.
The blue pimpernel (Anagallis cerulea), though not a native of England, is found occasionally. It is described as growing in beautiful little tufts about the hills of Madeira, and enlivening them by its cheerful colour, which may bear comparison with the azure of the sky.
