PLANT ASSOCIATIONS 227 



the ground was once or is stOI being periodically broken 

 by the plough and sown with seed. Even the moorlands, 

 where farmsteads are absent, have been interfered with 

 for the rearing and preservation of game. But the 

 greatest departure from the natural association is made 

 in cultivated ground regularly ploughed and sown with 

 crops. Here are found a number of agricultural weeds, 

 mostly annuals and aliens, which, following in the track 

 of civilization, have spread over all our arable fields and 

 the waste places near, where the ground is frequently 

 disturbed (see p. 215). 



Yet, in spite of all this interference by man, the depar- 

 ture from the natural association is really not very great. 

 The trees found growing in a plantation are trees which, 

 after rll, are suitable to the soil, and in many cases they 

 would be found growing there naturally. The flowers of 

 the field are wild, and the struggle for existence between 

 plant and plant, and association and association, goes on 

 much the same as if man did not interfere at all. Man 

 only modifies or assists the conditions under which Nature 

 acts ; he works and prepares the ground for the change 

 from one association to another (as in draining a marsh 

 or moor, or cutting down a wood), but the association 

 that comes in is natural enough in all its main characters. 



The chief associations belonging to each type of vegeta- 

 tion wiU be described later on, but, generaUy speaking, 

 any association should be examined frequently during the 

 year, and the following points recorded : 



1. The dominant plant or plants — i.e., the most 

 common or the most conspicuous plants. 



2. The sub-dominant plants, which accompany the 

 dominant forms, and, in a few places, supplant them. 



3. The other plants occurring in the association — ^noting 

 whether they are social or scattered, abundant, frequent, 

 local, rare, or casual. 



4. The succession of plants in flower throughout the 

 year. 



5. The number of different species in flower at the same 

 time. 



When two or more plants are dominant at the same 

 time, or when one plant is dominant at one time of the 

 year and others at a different time, the underground 

 parts of the plants should be examined, for the roots 



