Chapter II 



THE VARIOUS GROUPS OF PLANTS AND 

 HOW AND WHERE THEY LIVE 



Classification and Nomenclature 



To enable us to name and deal effectively with the almost infinite 

 variety of plants inhabiting the world, it is necessary to sort into 

 groups those which seem to have the closest affinity or, at least, 

 the greatest outward similarity. These groups in turn have to be 

 aggregated into larger groupings, and so on, to create a hierarchical 

 system of classification which we also like to think bears a close 

 relation to evolutionary history. Thus the members of a group 

 which look closely alike probably bear a ' blood relationship ' in 

 being descended from a common ancestor at no very remote period 

 of geological time ; indeed in some instances such a relationship 

 has been experimentally demonstrated. Biologists, and this includes 

 botanists, may in some cases disagree about the definitions, names, 

 and limits of this hierarchy of groups, but for general purposes 

 (and in descending order, from large to small) these groupings^ may 

 be listed as follows : 



Divisions or phyla (sing, phylum) : the major (highest) groupings 

 used in classifying plants, with names normally ending in -phyta, 

 those commonly recognized being the Schizophyta, Thallophyta, 

 Bryophyta, Pteridophyta, and Spermatophyta, and each consisting 

 of one or more 



Classes : the next commonly recognized units, plentifully 

 exemplified below, and each consisting of one or more 



Orders : each of which has its name ending in -ales, and in turn 

 consists of one or more 



Families : these, except in a few long-established instances, have 

 their names ending in -aceae. Usually the members of a family all 

 have some recognizable characteristic or characteristics, some com- 

 mon ' stamp ' ; they are grouped into one or more 



^ Also called taxa (singular taxou), regardless of rank. 

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