354 PLANT-LIFE 



reciprocal relations of organisms and the external world. 

 So far as plants are concerned, we will say tliat this new 

 and welcome science is the study of plants in their 

 haunts, or in relation to their environments. The 

 ecologist takes cognizance of plants in community rather 

 than as distinct individuals. As Warming, one of the 

 pioneers in the new botany, indicates, Ecology " teaches 

 us how plants or plant-communities adjust their forms 

 and modes of behaviour to actually operating factors, 

 such as the amounts of available water, heat, light, 

 nutriment, and so forth." We commonly differentiate 

 between the plants which are associated in distinct 

 habitats ; we talk about woodland plants, knowing that 

 in woodlands there are species peculiarly adapted to 

 flourish there, and forming a botanical community. If 

 we wish to secure a woodland species, we should not be 

 so foolish as to search for it in a salt marsh. We also 

 speak of the plants of the seashore, of the swamp, the 

 moor, heath, dune, and mountain, and in doing so form 

 in our minds more or less distinct pictures of communities 

 of plants characteristic of the sites mentioned. Now, 

 the ecologist seeks to know how it happens that certain 

 plants are associated in particular habitats, giving a 

 marked floristic physiognomy to the areas they occupy. 

 In making his inquiry he has to take account of numerous 

 factors. 



The first stage in the study of the plant-ecology of a 

 district consists in finding out what species are associated 

 in similar habitats. Take a moor here, and a moor 

 there, it is known that there are certain plants which 

 give a distinctive physiognomy to moors, and are to be 

 found in this or that patch of moorland. The ecologist 



