Domain of Physiology. 251 



name of physiology was given; and the two terms are in fact 

 synonymous. The study of nature, as has been shown, divides 

 itself into physiography and physiology; and this division 

 applies equally to each one of the three great kingdoms of 

 nature. Thus, for example, Physiographical Botany studies 

 the relations of plants to each other as members of the vege- 

 table kingdom, and investigates their external forms and 

 relationships, by which we arrive at Systematic and Descrip- 

 tive Botany with its classification and terminology. These 

 together give us Botany as a great division of Natural His- 

 tory. Physiological Botany, on the other hand, considers the 

 individual plant in itself, as seen in its structure, growth, and 

 development, and in its relations to the other kingdoms of 

 nature. It is properly divided into Structural Botany (which 

 investigates the anatomy, organography, and morphology of 

 the plant), and Vegetable Physiology (which studies the func- 

 tions of the vegetable organism, its growth, nutrition, and 

 decay, and the interdependence of the vegetable, animal, and 

 mineral kingdoms)*. The same distinctions and definitions 

 will apply, mutatis mutandis, to Physiographical and Physio- 

 logical Zoology. 



§ 31. The vastness and the complexity of the inorganic as 

 compared with the organic world of nature, makes it difficult 

 to grasp at once a conception of the true relations of Mine- 

 ralogy, which comprehends the study of all forms of unor- 

 ganized matter"j\ Physiographical Mineralogy, in its widest 

 sense, has thus for its object not only this earth, but all other 

 matter in space, and includes, so far as our planet is concerned, 

 Geognosy and Petrography, besides Systematic and Descrip- 

 tive Mineralogy as generally understood. 



§ 32. In the study of Mineralogy in its physiological aspect, 

 we have to consider the various conditions of mineral matter, 

 distinguished as gaseous, liquid, or solid, as amorphous, 

 crystallized in different geometric forms, or colloidal. These 

 unlike conditions of matter, and their different relations to 

 gravity, pressure, temperature, sound, radiant energy, elec- 

 tricity, and magnetism, the phenomena of capillarity, and of 

 the occlusion, diffusion, and transpiration of gases and liquids, 

 indicate structural, or, as we sometimes term them, molecular 

 differences in mineral species, which make up what we must 

 include under the title of Structural Mineralogy. 



The changes of mineral species from one condition to 

 another, and their transformations under the influences of 



* See Asa Gray, ' Structural and Systematic Botany,' Introduction, 

 t See- the author, on " the Objects and Methods of Mineralogy,' 

 Chemical and Geological Essays, p.' 453. 



U2 



