4 INTRODUCTION 



kinds of plants according to some system (whence the 

 term, systematic). 



(b) Taxonomy, or the principles of classification, based 

 upon the facts observed and their interpretation. 



(c) Nomenclature, the principles and rules adopted for 

 the formation and assignment of plant names. 



6. Morphology. — If, in our study, our attention is 

 centered chiefly on structure and form, our point of view 

 is that of morphology, and we recognize external and 

 internal anatomy, microscopic anatomy {histology), com- 

 parative morphology, experimental morphology (which 

 attempts to ascertain, by experiment, the causes of form 

 and structure), embryology (the study of embryos), and 

 other subdivisions. 



7. Physiology. — If we are interested primarily in w^hat 

 the various parts of the plant are doing, rather than in their 

 form and structure, our point of view is that of physiology. 

 We shall find, as we study, that the facts of form cannot 

 be understood or explained except in the light of the 

 physiological work of the given part; and conversely, 

 that physiological work cannot be explained unless the 

 structure is also understood. 



8. Ecology. — Every plant lives in a certain place, with 

 certain external surroundings; in other words it has a 

 home, or, as we usually say, a habitat or environment. 

 In order to live and keep healthy the plant must be 

 favorably adjusted to the various features (factors) of its 

 environment — the range of temperature, amount of light 

 and moisture, components of the soil, the earth's at- 

 traction (gravity), and surrounding animals and other 

 plants. The science of the relation of living things to their 

 environment is Ecology. 



