136 



COLLEGE BOTANY 



the nectaries of flowers aud in fruits, varying from one or two 

 per cent, in peaches to thirty per cent, in some varieties of grapes. 

 It also occurs in combination-forming glucosides. Glucose is the 

 first definite carbohydrate product of photosynthesis. 



(6) Levulose {fructose, fruit sugar, or levo-glucose) is asso- 

 ciated with dextrose and may occur in larger quantities. 



(c) Sucrose (saccharose , or cane sugar) is widely distrib- 

 uted, occurring in the stems of com, sugar cane and related 



plants; in the roots of some 

 plants, notably of the sugar 

 beet; in the cell sap of some 

 trees, notably of maples and 

 palms ; in the nectaries and 

 sap of some flowers; in some 

 seeds, such as the almond and 

 chestnut; and in many fruits. 

 This is the most important com- 

 mercial form of sugar, and is 

 obtained most abundantly from 



Fig. 93. — Cell from pea containing starch 

 and aleurone. 



sugar cane, sugar beets and 

 maple trees. 



(d) Maltose is formed in seeds, more especially the cereals 

 during germination. 



It will be readily seen that we secure a gi-eat deal of sugar 

 as food fro'm the ripe fruits that form such an important pari of 

 O'ur diet. Howeveir, man has learned to extract the sugar from 

 the sap of many plants, such as sugar caue, sugar beet and maple 

 trees. Sugar is easily digested and is a very important com- 

 pound in our food supply. 



Hemi or reserve celluloses are ver\' hard plant products 



