242 ORGANIC AGRICULTURAL CHEMISTRY 



Carbohydrates Present in Plants. — The more common 

 members of the carbohydrate group found in plants may be 

 given as follows: 



Hexose monosaccharoses, 



Glucose — Grape sugar 



Fructose — Fruit sugar 

 Disaccharoses, 



Sucrose — Cane sugar 



Maltose — Malt sugar 

 Polysaccharoses (not sugars), yielding hexoses, 



Starch 



Cellulose 



Dextrin 



Inulin 

 Polysaccharoses, yielding pentoses, 



Pentosans 



We find thus in plants all three of the main classes of this 

 group, viz. simple sugars or monosaccharoses, double sugars or 

 disaccharoses and compound sugars (non-sugar in character) or 

 polysaccharoses. All of these which are not hexoses themselves 

 are related to them and yield them on hydrolysis. In addition 

 to these we have also the polysaccharoses yielding pentose 

 sugars, i.e. the pentosans. In fact only three carbohydrates, 

 viz. glycogen, lactose and galactose, are found either exclusively 

 in animals or to a larger extent in animals than in plants. This 

 characterizes plants as the main and, with the exceptions cited, 

 the only source of the carbohydrates. 



Where, then, in the plant, do we find these different com- 

 pounds and how do they act as food ? In the leaves and other 

 green parts we find two of these carbohydrates in such conditions 

 that we are inclined to believe they are directly produced by 

 photosynthesis. These two are glucose and starch. 



Metabolic Transformations. — From our chemical study of 

 the carbohydrates we see that the relationship of the entire 

 group is such that in the living plant there is possible a con- 



