VEGETABLE CYTOLOGY 
83 
10. Saponin, another glucoside, found in f Soap Bark, Senega, 
Saponaria and other drugs also takes a red color with strong H 2 S 0 4 . 
11. Coniferin is a glucoside, occuring in the cell sap of the spruce, 
pine, and other plants of the Coniferce. If sections containing it are 
first treated with a solution of phenol and then with sulphuric acid, 
the cells containing it take on a deep blue color. 
12. Digitoxin, a glucoside found in the leaves of Digitalis purpurea, 
is colored green with hydrochloric acid. 
The glucosides are very numerous. Those listed above represent 
but a few examples. They arise in the cell sap of plants containing 
them as products of constructive metabolism (anabolism) and are 
thought by many to have the function of protecting plants against 
the ravages of animals. Some are known to serve as reserve food. 
All glucosides are characterized by the property of being split up 
into glucose and other substances when acted upon by a ferment, 
dilute acids or alkalies. 
13. Alkaloids. —Chemically, these are basic carbonaceous amines 
which like glucosides are products of metabolism. Their method 
of formation in plants is uncertain. Some hold that they are kata- 
bolic products, resulting from the breaking down of tissues, while 
others believe them anabolic in character. They undoubtedly serve 
as defensive agents in plants containing them on account of their 
bitter taste and poisonous properties. 
Properties of Alkaloids 
Alkaloids are invariably found in combination with acids forming 
salts which dissolve in water or alcohol. They are composed of 
carbon, hydrogen and nitrogen. Some contain oxygen. They are 
precipitated from saline solutions by the addition of alkalies. They 
are mostly colorless and crystallizable. They can be precipitated 
by one or more of the following alkaloidal reagents: tannic acid, 
gold chloride, phospho-molybdic acid, picric acid and potassio- 
mercuric iodide. 
Examples of Alkaloids 
Strychnine. —This alkaloid, with a chemical formula of C21H22N2- 
0 2 , occurs in the seeds of Strychnos nux vomica, Strychnos Ignatii 
and other species of Strychnos. When sections of strychnine con- 
