160 UNIVERSITY OF MISSOURI BULLETIN 



and probability from either a botanical or a zoological labora- 

 tory. Studies of the causes of variation and of the method 

 of organic evolution are cases in point. The right conception 

 of the situation is like the impression given by the dissolving 

 views of the stereopticon. 



The relation of botany to physics, chemistry, and meteo- 

 rology was brought out above in our study of Pleurococcus. 



If we would understand the method by which pollen is 

 transferred from one flower to another, or the nature and cure 

 of many plant diseases, we must join hands with the ento- 

 mologist ; in the study of fossil plants and of coal and graphite 

 the boundary between botany and geology is lost sight of; 

 the study of bacteria takes us into the realm of medicine, 

 hygiene, and sanitation; and the arch of agriculture is held 

 together by the keystone of botany. 



The dovetailing of one science into another is strikingly 

 illustrated in tracing various fundamental ideas and terms 

 to their origin. The chemist and physicist, for example, owe 

 the word gas to the first recorded experiment in plant physi- 

 ology.* 



It was Mariotte, known to most of you as the discoverer 

 of "Mariotte's Law" of gases, who first demonstrated that 

 the compounds found in plants enter the plant in simpler in- 

 organic form, and are elaborated into organic compounds 

 within the living tissue. It was Jan Ingen-Houss, a physi- 

 cian, who showed that the carbon dioxide of the air is the 

 source of the carbon in plants ; and we have to thank the 

 chemist, Liebig, for adducing the final evidence on this point, 

 and silencing forever the erroneous theory of the humus. 



The phenomenon of osmosis (the interchange of two 

 fluids when separated by a porous membrane), a purely non- 



*This experiment was performed by Van Helmont, the last 

 of the alchemists, and involved the burning of plant tissue. Since 

 most of the tissue passed away in an invisible form, Van Helmont, 

 being a Dutchman, called it the gaast or gas of the plant. We 

 recognize it today as carbon dioxide. 



