432 PROTECTION OF GREEN LEAVES AGAINST ATTACKS OF ANIMALS. 



little by oxen, horses, and sheep, not even by the omnivorous goat. As long as the 

 plants remain undisturbed in wood and meadow, their characteristic materials have 

 no effect on the olfactory nerves of men, but they must make themselves known to 

 the animals mentioned by the sense of smell, and this even before the plants have 

 been bitten and injured. The fact that plants which contain no alkaloids, and 

 generally are not poisonous to men, are at the same time carefully avoided by 

 grazing animals makes it probable that to eat them would be in some way injurious 

 to these animals. This remark applies particularly to mosses, ferns, succulent 

 plants (Sempervivum and Sedum), many cresses (Lepidium Draha, perfoliatum, 

 crassifolium), Toadflax (Linaria vulgaris), the Greater Plantain (Plantago Tnajor), 

 and many oraches. 



That horse-tails {Equisetum), the green leaves of the Crowberry and Bear- 

 berry {Emjpetrum and Arctostaphylos), the Rhododendron and Cowberry {Rhodo- 

 dendron and Vaccinium Vitis-IdcBa), and numerous other low evergreen shrubs, 

 which form a chief constituent of the vegetation of heaths and moors, as well as 

 the declivities of high mountains; further, that the Proteacese and Epacrideee which 

 compose the bush of Australia and the Cape, are avoided by the animals seeking 

 their food there, is indeed explained by the fact that the tissue of these plants is 

 very difficult to digest in consequence of strongly developed and partially silicified 

 cuticular strata. It is certain, therefore, that in the formation of a very thick, firm 

 cuticle, and in the deposition of silica in the cell-wall, a protective measure is 

 provided against the attacks of grazing animals; though, of course, it must not be 

 supposed that this is the only function discharged by these structures. 



In many plants water forms an excellent protection against grazing animals, 

 including that which falls as rain and dew on the foliage - leaves, and then 

 remains for days and even weeks collected in special hollows. In the morning 

 when the plants are richly bedewed, the ruminants do not usually graze; they wait 

 until the cold dewdrops and rain-drops which adhere to the leaves are evaporated; 

 and later also, they leave on one side those plants on which the rain-drops still 

 remain. In this respect the Lady's-mantle (Alchemilla vulgaris), known also in 

 popular language by the name of Dew-cup (illustrated in fig. 52^), is a very 

 striking instance. Rain and dew remain collected here at the bottom of the cup- 

 shaped leaves, when already, in the meadow round about, the surfaces of other 

 plants have become quite dry. While these latter, if they are not protected in 

 other ways, are devoured by the grazing animals, the Dew-cups remain undis- 

 turbed, and are evidently avoided. This is not caused, as in the ferns, by the 

 possession of certain objectionable materials — since the leaves of an Alchemilla, 

 from which the water has been shaken, are eagerly taken as food by the grazing 

 animals, which must, therefore, in some way dislike to feed on leaves on which 

 water is standing. 



The most important role in the defence against food-seeking animals is 

 performed by the organs terminating in strong, sharp, tapering points, which 

 wound offenders, and may be called the weapons of plants. In botanical 



