VEGETABLE CYTOLOGY 3 



10. Saponin, another glucoside, found in Soap Bark, Senega, 

 Saponaria and other drugs also takes a red color with strong H 2 SO4. 



11. Coniferin is a glucoside, occuring in the cell sap of the spruce, 

 pine, and other plants of the Conifera. 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 C 2 iH 22 N 2 - 

 O 2 , occurs in the seeds of Strychnos nux vomica, Strychnos Ignatii 

 and other species of Strychnos. When sections of strychnine con- 



