254 VEGETABLE PHYSIOLOGY 



characteristic decomposition without causing the incorpora- 

 tion of water during the process, thus : 



C 10 H, 8 NKSAo = C 3 H 5 CNS + C H, 2 C + KHS0 4 



Siiiigrin Sulpho-cyanate Glucose Potassium- 



of aUyl hydrogen- 



sulphate 



Others, such as rhamnase, existing in the seeds of Rhamnus 

 infectorius, erytkrozym in the Madder, gaultlierase in the 

 bark of Betula lenta, act on various glucosides, after the 

 manner of emulsin. 



The digestion of the glucosides, we may notice, is 

 always accompanied by the appearance of sugar, which is 

 one of the products of their decomposition. The fate of 

 the other bodies into which they split is not well ascertained, 

 though there is some evidence that cyanogen compounds, 

 even such as hydrocyanic or prussic acid, are used for 

 nutritive purposes by certain plants. 



The digestion of fat or oil has not been very fully 

 investigated, though certain facts are known concerning 

 its fate in germinating seeds. The digestion is generally 

 accompanied by the appearance of starch grains in cells 

 near the seat of digestion, and it was formerly considered 

 that the starch arose directly from the oil. It appears 

 now that the oil is split up by an enzyme, lipase, the result 

 being the formation of a free fatty acid and glycerine. The 

 subsequent decompositions are very complex, among the 

 products being lecithin, a peculiar fatty substance containing 

 phosphorus, as well as several simpler acid bodies, which 

 are crystalline instead of being viscid like the fatty acid 

 first liberated. These pass into the general body of the 

 seedling. The glycerine appears to contribute to the forma- 

 tion of the lecithin. The decomposition is. accompanied by 

 the appearance of sugars and starch, which are probably 

 formed by the protoplasm of the cells. 



Within the last few years it has been ascertained that 

 the production of alcohol from sugar is brought about by 

 another soluble enzyme, which has been prepared from 

 yeast. Though the existence of this body has been long 



