PLACE OF PLANT PHYSIOLOGY 5 



general scope of the subject, we can then divide our field very 

 easily into the pure and the applied botanical sciences. Pure 

 botany is the study of plants with no regard to their relations to 

 man but from the point of view of the plant alone. That is, in 

 pure botany all practical considerations, all benefits to man, are 

 out of the question; it is botany for botany's sake. Applied or 

 economic botany, on the other hand, is the study of plants with 

 a view to applying the knowledge gained to human needs. No 

 one would be so bold as to say that these lines are drawn sharply 

 in practice or even that they should be, but in theory these are 

 the limits. "Pure" botany is also an ill-chosen term because it 

 seems to imply that there is something more ennobling, more 

 scientific, and more honorable about the pure sciences than the 

 applied branches. Fortunately the number of scientists who con- 

 sider a thing bad because it is useful, is rapidly diminishing. 



To the subject of pure botany there are two great divisions. 

 First there are the subjects which deal primarily with structure 

 or composition, and secondly, those which deal with function or 

 operation, — the one group chiefly concerned with plant statics, 

 the other with plant dynamics. 



Morphology. — The structural subjects also fall into two cat- 

 egories. First one may consider the group of subjects which is 

 concerned with structure per se, and then the group which is con- 

 cerned with structures because of the light these studies throw 

 upon the problem of evolution. The first group makes up what 

 is known as morphology; while in the second category we have the 

 branches of systematic botany, whose business it is to reconstruct 

 the family tree of the plant kingdom. 



Morphology also may be divided into two groups of studies, — 

 those which consider structures primarily in their relation to 

 time and those which consider them primarily in relation to space. 

 Embryology is hence the study of the progressive changes in form 

 and structure during the development of a particular organism. 

 To be sure, space relations must also be considered, but the em- 

 phasis is placed upon the time element. 



Morphology from the point of view of spatial relations has 

 three main divisions: cytology, histology or minute anatomy, and 

 gross morphology. Cytology is the study of the cellular units of 

 the organism . Some cytologists may insist that their subject 

 is as much concerned with function as with form, and it can- 



