96 Chapters in Modern Botany CHAP. 



dies. Then the trunk becomes diseased, wood ants begin 

 their work, and finally nothing is left but the hollow 

 cylinder of the strangler." 



In the crowded vegetation by the river -side, in the 

 meadow, along the hedgerows, the same struggle for 

 standing room, for air, for light, must occur, and there are 

 many peculiarities of plants which find partial explanation 

 as adaptations of structure which help plants in crowded 

 places to keep their foothold. 



, When we remember that plants have not such diverse 

 needs as animals have; that they all require very nearly 

 the same kind of food; that most of them get this in 

 precisely the same way by their roots from the soil, by 

 their leaves from the air we feel that there must be what 

 may be called struggle or competition between them when 

 they grow crowded together. We get a vivid impression 

 of struggle for space in the crowded rosettes of a patch of 

 house-leeks (Sempervivums), which have been allowed to 

 grow for some time as they list ; we see the younger plants 

 budding from their parents, rising upon their shoulders, 

 and often not only smothering them, but soon coming to 

 crowd upon each other and compete anew. Again, only 

 a fraction of the seedlings which appear above the surface 

 in a plot of ground reach maturity. There is neither room 

 nor food for them all, and the less fit are eliminated. And 

 this is recognised practically by every farmer or gardener, 

 for does he not thin his turnips or onions, knowing that 

 thus alone can he ensure the success of individuals? 



No doubt there is some danger of exaggerating this 

 struggle for existence among plants, and yet more of 

 attributing to it results which may have some entirely 

 different origin. Experiment is much needed to sub- 

 stantiate what is often assumed. 1 But* on general grounds 

 1 A careful statement of facts was given by Mr. Walter Gardiner in 



