Page:Popular Science Monthly Volume 30.djvu/114

102 taller masses of may and holly. Nay, at times even naturally undefended species assume a protective armor under such special circumstances, as in the case of the pretty little pink rest-harrow, which grows close to the ground with soft stems and leaves where unmolested by cattle, but quickly develops an erect and stiffly thorny variety when invaded by troops of cows or horses. In that case the unarmed specimens get eaten down in a short time by the browsing cattle, and only those which happen to possess any slight tendency in a prickly direction are left to occupy the stubborn soil and produce seed for the next generation. It is this unconscious selective action of the larger herbivores which has at last produced the general prickliness of all the plants that naturally frequent rich and open lowland pastures.

There are differences, however, between prickles and prickles. Some plants are positively aggressive, like the stinging-nettle; others are merely and strictly defensive, like the common thistle, whose proud motto, as everybody well knows, is “Nemo me impune lacessit.” In the very doubtful Latinity of the Licensed Victualers, it goes in strictly for “Defensio non provocatio”; whereas the nettle, it need hardly be said, is often most distinctly provoking, and even goes out of its way to annoy a neighbor. This distinction I take to depend upon a difference in the acquired habits of the two races. The nettle is almost entirely a product of urban civilization; it hangs about the streets and out-houses of small villages, the neighborhood of farm-yards, and the immediate surroundings of rural man. It lives in constant expectation, as it were, of being browsed upon by donkeys, or trampled under foot by cattle, or picked by children, or stubbed up root and all by the ruthless farmer. Hence its temper has become permanently soured, and it has at last developed a restless, feverish, wasp-like habit of stinging everybody who comes within arm's length of it. It is necessary to the safety of the nettle, in fact, that it should give you warning of its presence at once, and induce you to keep well away from it under pain of a serious and lasting smart. Our common English nettle, which grows everywhere along road-sides and waste places, is bad enough in this respect; but the smaller nettle—a foreign importation of more strictly civilized and urban habits, never found far from human habitations—is still crueler and more poisonous; while the South European Roman nettle, accustomed for innumerable generations to the fierce struggle against Italian civilization, has developed an advanced and excruciating sting, which beats the puny efforts of our own species into complete insignificance, as the virus of the hornet beats the virus of the hive-bee.

On the other hand, the thistle family are far more truly rural and agricultural in their habits, being denizens of the open fields and meadows, less dependent than the nettles upon richness of soil, and readily accommodating themselves to all vacant situations. Hence they have only felt the need of arming themselves in a