' ' DEFENCE, NO T DEFIANCE. " 1 49 



These hairs vary in their character and density until 

 we find them passing into " prickles." Some species 

 have converted the hairs into " stings," as witness 

 the Nettles. No better illustration of the thorough 

 triumph of this contrivance could be afforded than 

 the abundance of Nettles by our waysides where 

 every other kind of vegetation has been cropped 

 and eaten by passing animals ; but the Nettles are 

 left alone, except by caterpillars. Not a few British 

 plants have learned the value of a Nettle neighbour- 

 hood, and are always to be found growing near or 

 even with them ; just as the helpless peasants grouped 

 themselves under the shelter and protection of the 

 barons' castles in the Middle Ages. 



In addition to those numerous and greedy enemies 

 of plants, the mammalia, vegetation has to be pro- 

 tected from another class of depredators — slugs and 

 snails. How voracious they are gardeners well know, 

 and accordingly set traps innumerable to catch 

 them, or arrange deterrents to keep them off In a 

 state of nature plants adopt the same device — 

 developing poisons in their tissues, or becoming 

 unsuitable to their molluscan appetites. A better 

 protection still is the formation of thorns and prickles^ 

 over which slugs and snails find it impossible to 

 trail their soft bodies without injury. In some 

 plants — the Brambles, for instance — these prickles 

 assist in climbing ; in others they keep off browsing 

 mammals as well as snails. 



