18 THE CHEMISTRY OF THE FARM 



plant food in the root, tuber, or stem, to serve for tbe 

 commencement of growth in the following spring. 

 In a biennial root crop — the turnip, for instance — the 

 root attains a great size in autumn, the leaves dying 

 after transferring to the root their most important 

 constituents. The next season the root throws up a 

 flowering stem, and the store of matter accumulated 

 during the preceding autumn is consumed in the pro- 

 duction of seed. With the production of seed the 

 root is exhausted, and the plant dies. 



In trees plant food is stored up at the end of 

 summer in the pith, the pith rays, and in the layer 

 between the wood and bark. The leaves which fall in 

 autumn have lost nearly all their starch, albuminoids, 

 phosphoric acid, and potash, these having been trans- 

 ferred to the stem. By the action of the sun in 

 spring-time the new buds swell, the sap rises, the 

 starch and other matters deposited in the wood during 

 the previous autumn are redissolved, and employed for 

 the production of new growths. The sugar found in 

 maple sap in spring-time results from the transforma- 

 tion of starch stored up in the preceding autumn. 



