178 PLANT PHYSIOLOGY 



rheumatism, and when hydrolyzed it breaks down into salicylic 

 alcohol (saligenin) and glucose : 



C13H18O7+H2O = C 7 H 8 2 +CHi 2 6 . 



The cyanophore glucosides yield HCN as one of their products. 

 The most common glucoside in this group is amygdalin, which 

 was one of the first glucosides isolated and which has probably 

 been studied more than any other. It has commercial value as 

 the essential material in oil of bitter almonds, which is much used 

 as a flavoring extract. When hydrolyzed by the enzyme, emulsin, 

 it breaks down into benzaldehyde, hydrocyanic acid, and glucose: 



C 20 H 27 NO 1 i+2H 2 O = 2C 6 H 12 O 6 +HCN+C 6 H 5 CHO. 



It occurs in almonds, in the seeds of apples, peaches, and plums as 

 well as in the leaves of cherries, peaches, and the cherry laurel, 

 where it is often the cause of stock poisoning as a result of the 

 liberated HCN. The enzyme and glucoside are evidently kept 

 apart in the cell under normal conditions and not till the cells are 

 crushed and eaten does the hydrolysis result. 



Among the mustard-oil glucosides may be mentioned sinigrin, 

 which occurs in mustard, horse-radish, etc. When hydrolyzed 

 by the enzyme, myrosin, it is broken down into glucose, mustard 

 oil, and acid potassium sulphate : 



Ci H 16 O 9 NS 2 K+H 2 O = C 3 H 5 NCS+C 6 H 12 6 +KHS0 4 . 



The saponins form another important group of glucosides. 

 They are amorphous, colloidal substances which produce a soapy 

 froth when dissolved in water. When shaken with fats and oils 

 they produce a stable emulsion, enabling them to be used as soap 

 substitutes, and it is from this property that the name saponin 

 comes. The watery solutions of saponin also have the property 

 of dissolving large quantities of gases such as carbon dioxide, and 

 they are occasionally used in soft drinks for this purpose, although 

 this should be discouraged because the saponins are toxic, produc- 

 ing hemolysis (dissolution of the red corpuscles). Fish are espe- 

 cially sensitive to such toxins and are killed by a solution of one 

 part in a hundred thousand. In certain regions of the East sapo- 

 nins are used for this purpose. They have been found in several 

 hundred plants scattered throughout the plant kingdom and may 



