CHAPTER XIV 



THE ECOLOGICAL CLASSIFICATION OF PLANTS 



1. The Ecological Groups 



In the four preceding chapters the plants of the earth were 

 considered phylogenetically, that is, according to their relation- 

 ships ; but incidentally they were also described ecologically, 

 that is, according to their fitness to their surroundings. Of 

 this fitness the most important phase concerns their habits, 

 viz. the way they live in the places they do. Now plants 

 which have habits in common constitute ecological groups, and 

 these ecological, or habit, groups collectively make up the 

 orderly vegetation of the earth, precisely as the phylogenetic 

 groups make up its flora (page 392). Thus plants are also 

 classifiable ecologically, as we have now to consider. 



The comparative study of plants shows that no necessary 

 connection exists between relationship and habit. Relation- 

 ship is a matter of heredity, which mostly shows best in 

 connection with the reproductive parts of plants (page 392), 

 but habit concerns chiefly the vegetative organs, — leaves, 

 stems, and roots. Some of the habit, or ecological, groups have 

 already been mentioned, — e.g. Xerophytes, Hydrophytes, and 

 Mesophytes on page 190, with Climbers and Epiphytes on pages 

 184-5. Such groupings correspond with those of men into 

 trade unions, professional associations, etc., all the mem- 

 bers of which possess in common such characteristics and 

 interests as have essential connection with their mutual 

 occupation, though none may be blood relatives at all. It 

 is true, in large measure the phylogenetic and ecological 

 groups are coincident, especially among the lower forms, 

 just as members of the same family among men, particu- 

 larly of primitive races, tend to follow the same occupation. 



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