102 THE POPULAR SCIENCE MONTHLY. 



taller masses of may and holly. Nay, at times even naturally unde- 

 fended species assume a protective armor under such special circum- 

 stances, as in the case of the pretty little pink rest-han*ow, 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 cow r s or horses. In that case the unarmed speci- 

 mens get eaten down in a short time by the browsing cattle, and only 

 those which happen to possess any slight tendency in a prickly direc- 

 tion are left to occupy the stubborn soil and produce seed for the next 

 generation. It is this unconscious selective action of the larger herbi- 

 vores 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 con- 

 stant 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 per- 

 manently 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 com- 

 mon 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 sti' 1 crueler and more poisonous ; 

 while the South European Roman nettle, accustomed for innumerable 

 generations to the fierce struggle against Italian civilization, has devel- 

 oped an advanced and excruciating sting, which beats the puny efforts 

 of our own species into complete insignificance, as the virus of the hor- 

 net 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 rough-and- 



