PROTECTION OF GREEN LEAVES AGAINST ATTACKS OF ANIMALS. 431 



in the destruction of their food-plants, their own existence is imperilled. If man 

 removes a portion from the plants serving for his livelihood, a limit is always fixed 

 to this consumption which prudent consideration and foresight never overstep. He 

 always leaves as much as is necessary to the plant in order that it may maintain 

 itself and multiply. Indeed, he even tries to assist and to further the nourishment, 

 growth, and multiplication of the plants useful to him, and is at considerable 

 trouble to protect and to save serviceable vegetation from the ravages of animals. 

 This protection of man, however, is limited to a comparatively small section of 

 plant species; all those from which he derives no benefit remain uncared for, and 

 these would be surrendered to the overwhelming onslaughts of animals, and final 

 destruction, if means were not at their disposal by which they could protect and 

 maintain themselves. Of course these means are not adapted to offensive attacks 

 upon the animal kingdom; and the attitude of the vegetable world towards animals 

 must not be looked upon as one of war, but rather as an armed peace. 



But if plants have only at their disposal means of defence, these are none 

 the less dangerous to oftenders, and not only equipments comparable to pointed 

 weapons, but also poisons and corrosive fluids are abundantly turned to account. 



First of all, with regard to 2^oisons. It is to be pointed out that these are only 

 developed in those parts and to an extent necessary in order to preserve at least the 

 greater portion of the foliage, and then also the flowers and fruit. Moreover, it 

 must be remembered that the same chemical compound does not act as a poison to 

 an equal degree in all animals. The foliage of the Deadly Nightshade {Atropa 

 Belladonna) is a poison to the larger grazing animals, and by them is left undis- 

 turbed; but the leaves of this plant are not only non-poisonous to a small beetle 

 (Haltica Atropce), but form this animal's most important food. The larvte of this 

 beetle often eat numerous holes in the leaves, which, however, by no means prevent 

 the development of the Deadly Nightshade. Accordingly these leaves are protected 

 by the alkaloid contained in them only against wholesale extermination ; limited 

 portions of them can be surrendered and sacrificed with impunity. The same 

 thing occurs in numerous other plants which contain poisonous alkaloids, or other 

 materials harmful to large herbivorous animals. It is puzzling how gi-azing 

 animals find out the materials in the leaf which are injurious to them. In many 

 instances the plants in question possess characteristic odours which act offensively 

 on the olfactory nerves of men at any rate, as, for example, the Thorn-apple 

 (Datura Stramonium), the common Henbane (Hyoscyamus niger), the Hemlock 

 {Conium maculatutn), the common Birthwort {Aristolochia Clematitis), the Dwarf 

 Elder (Sambucus Ehulus), and the Sabin {Juniperus Sabina); many other poisonous 

 species, however, which are likewise avoided by grazing animals, bear leaves which 

 to men are odourless as long as they are intact — as, for example, the numerous 

 species of Monkshood {Aconitum), Black Hellebore {Helleborus niger), the White 

 Hellebore {Veratrum album), the Meadow Safiron {Colchicum autumnale), the 

 Mezereon {DapjKne Mezereum), species of Spurge {Euphorbia) and Gentians 

 (Gentiana), which are never disturbed by stags, roes, chamois, hares, and just as 



