ECOLOGY. 3 ot 



563. In carrying on studies of this kind one should bear in 

 mind the factors which influence plants in these relationships, 

 that is, what are called the ecologic factors ; in other words, 

 those agencies which make up the environmental conditions of 

 plants, all of which play a greater or lesser role in the habit or 

 status of the plant concerned, and which, acting on all plants 

 concerned, give the peculiar color or physiognomy to the plants 

 of a region or of a more restricted community. 



Such factors are climate, with its modifying meteorological 

 conditions ; texture, chemistry, moisture content, covering, to- 

 pography, exposure, etc. , of the soil ; influence of light and 

 heat ; of animals, of plants themselves, and so on. 



