34 
PLANT MORPHOLOGY. 
tile oils are characteristic of some of the largest families 
of plants, as the Compositae, Labiatee, Rutacese and 
Umbelliferse. 
The oils, both fixed and volatile, are insoluble, or 
nearly so, in water; but are soluble in ether, carbon 
disulphide, chloroform, benzin, benzol and acetone. 
Most of the volatile oils and a few of the fixed oils are 
more or less soluble in alcohol. They are colored 
brownish or brownish black with osmic acid. The 
volatile oils are stained red by alcoholic solutions of 
alkanet, and some of them by certain of the aniline 
dyes, as fuchsin. The distinctive test for the resins is 
that when treated with concentrated aqueous solutions 
of copper acetate they acquire a green color. They 
are likewise stained blue by Hanstein’s aniline violet. 
The reserve or fixed oils are liberated as oily globules 
on treatment of sections with sulphuric acid or concen- 
trated chloral solution. 
The volatile oils are not infrequently associated 
with other substances of the plant cell in varying pro- 
portions, as resins, gums, and certain acids of the aro- 
matic series, as cinnamic and benzoic. Those products 
which consist chiefly of oil and resin are known as oleo- 
resins, and include turpentine and copaiba ; those 
consisting chiefly of gum and resin and containing but 
little volatile oil, are known as gum-resins, and include 
ammoniac, asafetida, galbanum and myrrh ; oleo- 
resins associated with aromatic acids are known as 
balsams, as balsam of tolu, balsam of Peru, storax and 
benzoin, which latter is usually called a balsamic resin. 
3. THE FERMENTS OR ENZYMES. 
The ferments or enzymes are apparently associated 
with the protoplasm, though, like other constituents, 
they may be found dissolved in the cell sap. In some 
