BOTANY 159 



made necessary because of the limitations of the human mind. 

 No actual boundary lines exist. 



The science of living things is biology, and it is consid- 

 ered by many that botany and zoology taken together con- 

 stitute the science of biology. I should prefer to consider 

 botany, zoology, and biology as three sciences, each distin- 

 guished by a separate aim. The ultimate aim of botany is 

 to answer the question what is a plant?; of zoology to an- 

 swer the question what is an animal ? ; but the aim of biol- 

 ogy is to answer the question what is life? The biologist, 

 to be sure, must study life as manifested in living things, 

 some of which are plants, and some animals, but I feel very 

 certain that the main question of biology would not be half 

 answered if we were able to frame a complete definition 

 of either a plant or an animal. 



Thus the question of how plants respire is purely bo- 

 tanical ; the question of how animals respire is purely zoolog- 

 ical. The answer to one of these questions might throw 

 more or less light upon the other. From the standpoint of 

 biology, however, the question becomes what is respiration? 

 To answer it the process must be comparatively studied in 

 both plants and animals. 



But here, as elsewhere, it is by emphasizing the essential 

 unity, rather than diversity, that we keep closer to fact, and 

 further clear thinking. It must be emphatically insisted that 

 such subdivisions of knowledge are merely mental formal 

 conveniences, with no existence in reality; for while we may 

 conceive of three distinct aims, as indicated above, there are 

 innumerable investigations that might be carried on with 

 equal propriety, with either aim in view. And, furthermore, 

 it is impossible to pursue intelligent research in many phases 

 of either biology, botany, or zoology without understanding 

 and regarding results obtained in all three branches. It is 

 as significant as noticeable how many scientific papers of re- 

 cent publication might have emanated with equal propriety 



