CHAP. VII Relations Betzveen Plants and A nivials 121 



Vegetabilia, with or without a common debatable land of 

 Protista (or it may be a still more fundamental, albeit in 

 its own way strangely specialised group of Myxomycetes\ 

 is an important controversy enough, yet after all a mere 

 internal problem for biologists to settle among themselves. 



Recognising then plants and animals as two main 

 groups of living creatures, which in their life have to solve 

 essentially the same problems, we may profitably continue 

 to study the many points of contact between them, inter- 

 relations such as those which we have already described 

 between insectivorous plants and their prey. Illustrations 

 of these interactions are growing increasingly numerous. 



The seedlings, whose struggle for existence Darwin was 

 fond of watching, were sometimes thinned by one another, 

 and sometimes by the weather, but often by slugs, insects, 

 and other animals. This is of course the most obvious of 

 relations ; hosts of vegetarian animals feed upon plants. 

 Nor is this relation so one-sided as it looks, for in so doing 

 the animals are often of real service. The thrush which 

 eats the mistleto-berries spreads the undigested seeds from 

 tree to tree ; the bees which rob the flowers of their nectar 

 are at the same time the bearers of fertilising pollen from 

 plant to plant ; even the cattle which wholly eat up some 

 kinds of herbage give others more room in which to grow. 



That animals select one kind of plant and leave others 

 untouched is an undoubted fact, and it is easy to believe 

 that this selective process may have many important 

 results. Let us take the case of snails and plants which 

 was studied in great detail a few years ago by Professor 

 Stahl,^ the experimental lichenologist already quoted. 



Plants and Snails. — There are two kinds of snails — 

 omnivorous eaters and " specialists," as Stahl calls them. 

 The latter are epicures, feeding daintily on toadstools and 

 ^ PJIanzefi und Schnecketi , 8vo, Jena, 1888. 



