VEGETATION. 349 



been formed in the spring becomes harder by continued 

 woody deposit. At length, however, there ceases to be any 

 formation of wood, and in its stead starch is made, and dif- 

 fused through every part of the plant by the autumnal sap, 

 the buds of the next year being formed at the same time. 

 In the following spring this starch thus stored up is con- 

 verted into dextrine and sugar, from which the leaves and 

 tender branches are constructed, and the whole plant in- 

 creased in bulk. 



QUESTIONS. 



471. What is said of the dormant seed, and of its stimuli? What are 

 the constituents of the seed ? What changes do the stimuli effect in these ? 

 472. What familiar examples have we of such changes? 473. State the 

 contrast between the formation of the lead-tree and that of the root and 

 germ of the plant. From whence are the materials for their growth de- 

 rived? 474. What is said of the supply of carbon to plants? 475. What 

 of the sources of their oxygen and hydrogen ? What is said of the decom- 

 position of water in plants and in the laboratory of the chemist ? 476. 

 Explain how plants can grow without earth. In what respects is their 

 growth defective, and why ? 477. What is said of the nitrogen in the air 

 in relation to the supply of plants with it ? From what source is it sup- 

 plied, and how ? What is said of the presence of carbonate of ammonium 

 in the air? 478. Give the summary in regard to growth and decay. 479. 

 What is said of nitric acid as supplying nitrogen to plants ? 480. What is 

 green manuring? How does it fertilize land? 481. What is said of the 

 inorganic food of plants ? 482. What of the ashes of plants ? 83. Of 

 what use is the chemical examination of the ashes of plants to the culti- 

 vator? What are Liebig's three classes of plants ? 484. What are the 

 offices of water in plants ? What is said of the quantity of water that 

 circulates in them ? 485. WTiat provision is made by annual plants for 

 the following year ? What is the provision in perennial plants ? 



