PART II 



ECOLOGY 



CHAPTER XXIV 

 PLANT SOCIETIES 



377. Ecology. Plant ecology includes all that portion 

 of botany which has to do with the way in which plants get 

 on with their animal and plant neighbors, and especially 

 the way in which they adjust themselves to the nature 

 of the soil and climate in which they live. Ecology, in 

 short, discusses the relations of plants to their surround- 

 ings or environment. A good deal of what has been said 

 in previous chapters about such topics as parasitic plants, 

 the occurrence of winter bud-scales, the movements of 

 leaves, the coating of hairs on stems and leaves, the 

 storage of water in epidermis-cells, is really ecological 

 botany, although it is not so designated in the sections 

 where it occurs. 



378. Plant Societies. In a single acre of woodland, 

 of marsh, or of meadow, there will usually be found a 

 large number of species of plants. One species may be 

 sufficiently abundant and conspicuous to give a name to 

 the whole tract, so that it may, for instance, be recognized 

 as a bit of birch wood or of cat-tail swamp. But under 

 the birches and among the cat-tails there are plants, it may 



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