PLANT DEVELOPMENT. ]5 



With a biennial or perennial crop the case is somewhat 

 different. The first development of root and leaf is the 

 same as in an annual; but towards the end of summer 

 there is a storing up of concentrated plant food in the root, 

 tuber, or stem, to serve for the 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 flower 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 transferred 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 re-dissolved, 

 and employed for the production of new growths. The 

 sugar found in maple sap in spring-time results from 

 the transformation of starch stored up in the preceding 

 autumn. 



