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 w T ork, 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. 
