134 The Department of Plant Physiology [332 



sider the processes that go on in inanimate things. Indeed, 

 the close relation between the physiology of animals and that 

 of plants is becoming so well appreciated in recent years that 

 a science of general physiology (dealing with the physics and 

 chemistry of all living things) appears to be rapidly devel- 

 oping. It is seldom possible to treat any physiological topic 

 adequately without reference to both plants and animals. 

 Some of the topics dealt with in plant physiology may be 

 mentioned as examples. Such are: water requirement; nu- 

 trition by inorganic materials; nutrition by organic ma- 

 terials; the exchange of energy between the organism and 

 its surroundings; the chlorophyll function; respiration, with 

 and without free oxygen; enzymes, activators, hormones, and 

 the general phenomena of catalysis; the control of growth 

 and development, including reproduction; the physiology of 

 movement and its control, and the physics and chemistry of 

 protoplasm. 



The non-physiological aspects of biology may be grouped 

 together as morphology, which deals with the structures of 

 organisms. Perhaps one of the most noticeable aspects of 

 physiological endeavor, and one in which it differs remark- 

 ably from morphological study at the present time, is this, 

 that it has little to do with the general problem of evolu- 

 tion and phylogeny. Evolutionary philosophy has been 

 built up largely from morphological observations, and it is 

 only recently that it has become possible to relate different 

 organisms to each other with reference to their physical and 

 chemical processes. The evolution of animals and plants has 

 never yet been one of the main topics of physiology. 



The sciences of mycology, bacteriology, pathology, ecology, 

 etc., all have their morphological and physiological aspects, 

 and their subject-matter may be treated from the stand- 

 point of static description or from that of process dynamics. 

 Thus, that branch of pathology which deals with the identi- 

 fication of parasitic organisms is mainly morphological in its 

 point of view, while the sciences of toxicology and immunology 

 are clearly branches of physiology. It is not without sig- 

 nificance that many of the characters by which the bacteria 



