2 Introdiiction 



depends upon them in his primitive relations to nature. 

 In their more obvious forms, therefore, the units of vege- 

 tation have common names in all languages, and these 

 are everywhere preserved in the names of places. Wood, 

 moor, heath, marsh, are some of the commonest and most 

 obvious examples. Now it is to be observed that most 

 of these names refer to something more than the vegeta- 

 tion alone. A moor is an area supporting certain kinds 

 of plants, but it also implies the presence of a peat-soil 

 on which those plants flourish. Heathland nearly always 

 involves a relatively poor and dry soil. A marsh is an 

 area where the soil is always wet. In other words a 

 vegetation-unit is always developed in a habitat of definite 

 characteristics. 



To look at the matter from the opposite standpoint, 

 synthetically instead of analytically, certain kinds of 

 plants are always found associated together under definite 

 conditions of life, and such groupings may be called 

 plant-communities. A plant-community is simply a vege- 

 tation-unit regarded as an aggregation of species and 

 individuals instead of as a division of the whole vegetation 

 of the region. Whichever standpoint we adopt, the 

 connexion with habitat is a fundamental part of the 

 conception. This way of considering the distribution of 

 plant-life is called ecological plant-geography, from the 

 Greek oTkos, a house (habitat), in contradistinction to the 

 floristic plant-geography, referred to above, which is 

 concerned primarily with the distribution of species. 



Ecology includes more than the study of vegetation- 

 units or plant-communities; it deals with the whole of 

 the relations of individual plants to their habitats. This 

 latter branch evidently cannot be sharply separated from 

 physiology; and may in fact be justly considered as a 

 part of that subject. It has been aptly called by Professor 

 Schroter of Zurich autecology, to distinguish it from syn- 

 ecology or the study of plant-communities. 



