PROTECTION OF GREEN LEAVES AGAINST ATTACKS OF ANIMALS. 451 



On the forest pasture of the Lower Alps often all that is to be seen covering the 

 ground are mosses and ferns, which are offensive to the animals, along with the 

 bitter Gentiana asclepiadea and Aposeris fcetida, abounding in a malodorous milk, 

 detested by all ruminants. In some meadows in the Central Alps the fern 

 Allosorus crispus, and with it the Mat-grass (Nardus stricta), are so prominent that 

 scarcely any other species of plant are to be seen there. Again, in other places, the 

 ground is overgrown with the Bracken fern (Pteris aquilina), detested by grazing 

 oxen, and also with prickly juniper-bushes. On the cultivated grounds near Trieste 

 the stiff, prickle -leaved and steel-blue Eryngium {Erynginm amethystinura) 

 impresses one by its profusion. In the Hungarian uplands one may recognize the 

 spots where cattle are kept by the abundant occurrence of Xanthiumn spinosuTn and 

 EryngiuTn campestre, of tall thistles and of Mullein, of Thorn-apples and Hen- 

 bane, and of several species of spurge, which are only eaten by the animals under 

 the greatest stress. It is thus shown by a hundred examples that in tracts exposed 

 to the pasturage of larger animals, those plants always obtain the upper hand which 

 are not attacked by the animals, in consequence of their poisonous and disagreeable 

 properties, or because of their defensive spines and prickles. 



A phenomenon connected with the conditions here described deserves mention. 

 This is the regular occurrence of defenceless plants under the protection of those 

 which are provided with abundant means of defence. Thus certain wild vetches 

 and Umbellifers (species of Vicia, Lathy rus, Anthriscus, Myrrhis, ^gopodium, 

 Cheer ophy Hum, &c.), which would furnish very good fodder for grazing mammals, 

 are regularly seen in the prickly hedges along the roads, and under spiny bushes, 

 which form a belt around forests. The bushes defend not only their own foliage, 

 but also that of the delicate vetches and Umbellifers which have established them- 

 selves under their protection. In neighbourhoods where the primeval character and 

 distribution of the vegetation is almost entirely lost, the companionship of certain 

 plants is so general that one might be tempted to regard it as a symbiosis. Here, 

 however, this is certainly not the case, for the advantage is all on one side^that 

 of the plants protected; while the bush, armed with spines against the assaults of 

 animals, under whose branches the defenceless plants have grown up, receives no 

 thanks, no profit, and no return from them, and certainly does not afford the pro- 

 tection intentionally. 



