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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