488 THE SPECIFIC CONSTITUTION OF PROTOPLASM. 



(Thymus Chamcedrys, montanus, vulgaris, Zygis, &c.), each will give off a peculiar 

 scent; and when the roots or root-stocks of different Valerians (Valeriana celtica, 

 dioica, elongata, officinalis, Phu, saxatilis, &c.), or of different species of the Asara- 

 bacca genus (Asarum Canadense, Europceum, &c.) are dug up, though they all 

 smell of valerianic acid or spikenard, each species has in addition a distinctive 

 odour of its own. The edible Fungi (Polyporus conftuens, frondosus, ovinus, &c.), 

 Garlics (Allium ascalonicum, Cepa, Porrum, sativum, Schoenoprasum, &c.), 

 various Currants (Ribes alpinum, petrceum, rubrum, &c.), and the Strawberries 

 (Fragaria collina, elatior, grandiflora, vesca, &c.) all demonstrate most decisively 

 that our olfactory nerves can distinguish between the different species of some 

 genera. It might also be pointed out that it is no infrequent occurrence for one 

 species of a genus to be poisonous to man while another is harmless, e.g. species 

 of the Star- Anise genus (Illicium anisatum and religiosum), and of the fungal 

 genus Lactarius (Lactarius deliciosus and torminosus). It is familiar to naturalists 

 how precisely herbivorous animals can distinguish between different species of 

 plants. The caterpillar of the Oleander Hawk-moth (Sphinx Nerii) lives exclu- 

 sively on the Oleander (Nerium Oleander), that of a small Mediterranean butterfly, 

 Thais Hypermnestra, only on the Birth wort (Aristolochia Clematitis), that of 

 the small Tortoise-shell Butterfly (Vanessa Urticce) only on the leaves of the large 

 Stinging Nettle, and that of Libythea Celtis only on the foliage of the Nettle-tree 

 (Celtis australis). Each caterpillar can at once distinguish the only species which 

 suits it from numerous other similar ones. A friend of mine once found the 

 caterpillar of a butterfly he did not know high up on the Gletscherstock in the 

 Stubai, Tyrol, which he took into the valley with him intending to feed it until 

 it became a chrysalis in order to obtain the butterfly. In the valley he placed it 

 on about a hundred different plants in the hope that it would settle on one or 

 other and use it as food. But it would not touch one of them, although caterpillars 

 apparently suffer from voracious appetites. My friend now determined to revisit 

 the spot where he had found the caterpillar and to set it at liberty there. When 

 he did so it at once crawled as quickly as possible to a certain plant (Cardamine 

 alpina) and attacked it with great eagerness. Later he discovered it to be the 

 caterpillar of Pieris Callidice, which only feeds on the small Alpine Bitter-cress 

 (Cardamine alpina). Generalizing from these instances, many more of which 

 might be given, we are justified in assuming that the aromatic substances, alka- 

 loids, acids, &c., which are manufactured in the plant metabolism are quite definite 

 for each particular species. But it is equally obvious that a specific protoplasm is 

 necessary for the manufacture of specific substances, or, in other words, that each 

 plant-species with a certain definite form possesses also a definitely constituted 

 protoplasm of its own. 



The behaviour of different species with regard to temperature is especially 

 worthy of note among the many observations which support this view. It is well 

 known that seeds of various species which closely resemble one another in outward 

 appearance differ greatly in the temperature they require for germination. Seeds 



