136 



COLLEGE BOTANY 



the nectaries of nowers and 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 corn, 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 

 pa.lms ; 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 SllgRF Cane, SUgOT beets and 

 and aleurone. 



maple trees. 



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

 during germination. 



It will be readily seen that we secure a great deal of sugar 

 as food from the ripe fruits that form such an important part of 

 our diet. However, man has learned to extract the sugar from 

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

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

 pound in our food supply. 



j&emt or reserve celluloses are very hard plant products 



