OFFICE OF THE ROOT. 347 



872. The agency of the leaves of 



the , 



of plants in absorbing and decomposing car- 

 ro- bonic acid > ma y be illustrated by the simple 

 ved by experi- means represented in the figure. A glass 

 funnel being filled with leaves, and slightly 

 carbonated water, is exposed to the sun. 

 Oxygen gas is gradually evolved from 

 the absorption and decomposition of the 

 carbonic acid, and collects in the tube 

 of the funnel. The oxygen may be 

 tested by the usual means. The inversion of the fun- 

 nel without loss of its contents, is easily effected, by 

 covering it with a saucer and turning it in a pail of 

 water. 



873. For certain transformations of ma- 



What trans- . . . 



formations oc- terial in plants, the evidence is entirely con- 



purin plant*? clusiye> The sugar beet and tumip are 



sweetest in the earlier stages of their growth. Later 

 in the year they become hard and fibrous. This change 

 is undoubtedly owing to the conversion of the sugar, 

 contained in the sap, into woody fibre. In the ripening 

 of grain, the sweet and milky juice of the young plant 

 is converted into starch. Both hay and grain, which 

 are harvested too late, are deteriorated by the conver- 

 sion of a portion of their starch and sugar into wood. 

 In the ripening of fruits a portion of their acid is con- 

 verted into sugar, as is evident from their change of flavor. 



874. OFFICE OF THE ROOT. The agency 

 How w the ac- o f fa e roo t s m supplying the plant with its 



tion of the 



roots'illus- mineral food, may be illustrated by the 

 apparatus represented in the figure. In 

 preparation for the experiment, a glass fun- 



