

PLANT ANALYSIS AS AN APPLIED SCIENCE 179 



cell wall, and from carbonaceous substances, such as sugar, 

 fats, and acids. It was stated that the volatile part of plants 

 on incineration is gaseous, consisting principally of carbon 

 dioxide, watery vapor, and nitrogen, the inference being 

 that the combustible portion of the plant contains the elements 

 carbon, hydrogen, and nitrogen. 



The fact that various mineral constituents are essential to 

 the growth and development of plants is of practical value in 

 agriculture. The soil must contain the various constituents 

 in such quantity and form as to be available to the plant. 

 The ash analysis of any plant indicates in a great measure 

 the character of its surrounding soil, though the chemical 

 composition in which the ash is contained in the plant is not 

 necessarily the same as in the soil. 



In investigating a new plant for the first time, all rational 

 means for discovering its component parts should be resorted 

 to. Before beginning the systematic analytical scheme, a micro- 

 chemical investigation of thin sections of the plant, and even 

 of the powdered plant, may be followed. I have found it an 

 excellent aid in the work, after knowing what constituents 

 were present from chemical analysis, to determine in what 

 tissues and cells these various substances are found. A drop 

 of the extracts evaporated on a glass slide frequently indicates 

 the character of the substances contained in them. 



It is of importance to determine if volatile oils or acids, 

 alkaloids, and other substances are present, which can be 

 separated by distillation, and for this purpose a sufficient 

 quantity of the powdered plant may be mixed in a convenient 

 vessel with water, acidulated water, or milk of lime, and the 

 mixture heated, preferably by steam. The distillate is con- 

 densed and may be examined as to its reaction, odor, and 

 physical appearance. If the aqueous distillate is agitated with 

 a light pretroleum- ether, 1 volatile products may be readily 

 obtained. 



Many volatile oils diffuse in moist air and pass off with the 

 petroleum- ether, if precautions are not taken to prevent it; 



1 Manufactured by Dr. H. W. Jayne, Frankford, Pa. 



