HOW PLANTS ARE CLASSIFIED 197 
184. Divisions upon bases other than structure. As already 
suggested (section 181), plants may be grouped upon the basis 
of their place of living or mode of life. Also, sub-divisions of 
the study of plants may be designated by the particular point 
of view that is kept in mind in pursuing the study. The study 
of the classification of plants into their proper groups and the 
determination of their proper generic and specific names is 
called taxonomy, or systematic botany. When emphasis is placed 
upon a comparative study of plant organs and their relation- 
ships, the study is known as plant morphology. Special study 
of the cell is cytology. Plant activities or work and their rela- 
tions to the immediate surroundings of the plant are included 
in physiology, while the relationships of plants to one another 
and to the environment in general is ecology. One phase of 
ecology deals with the distribution of plants over the earth 
and is known as ecological plant geography. The study of plant 
diseases is known as phytopathology, or plant pathology. A 
study of the bacteria constitutes bacteriology. A consideration 
of the useful or harmful aspects of plants is included under 
the general term economic botany, and under this head there 
are such sub-divisions as agricultural botany and horticultural 
botany. These are but the leading aspects under which plants 
may be studied. 
It is evident that these divisions have no sharply marked 
lines between them, and that they are not all made upon the 
same basis. For example, we might study the bacteria with 
reference to their structure, which would be morphology ; or 
in their relation to disease, which would be pathology; or in 
their relation to farm and garden crops, which would be 
economic botany. 
185. Names necessary as labels. In the following chapters 
we shall study a few representatives of the leading great 
groups of plants. It is necessary to have specific names for 
the plants that are used as illustrations of these groups, for 
sometimes the plants used do not have common names, and 
sometimes the common names, when used, are applied to two 
