4 Feeds and Feeding. 



substance by the energy of sunlight and heat guided by the life 

 principle of the protoplasm with its chlorophyll. The result of 

 the union of the gas and water is starch, with some oxygen left 

 as a by-product. The oxygen escapes to the air, while the starch 

 is retained by the plant for manifold uses. It is possible that 

 starch is not the first substance formed, but it is the first with 

 which we have to deal. 



6. Starch. The great building material of the plant is starch. 

 The plant has use for little or none of the starch in the cells 

 where it is manufactured, but requires it elsewhere. Being insol- 

 uble in water and forming in cells which are closed sacs, the 

 starch cannot be transferred to other parts of the plant in its 

 original form. The difficulty is overcome by the protoplasm of 

 the cell changing the starch into sugar and soluble substances 

 closely allied to starch, as we shall presently see. Sugar is solu- 

 ble in the juices of the plant, and by diffusion it is readily trans- 

 ferred from cell to cell until it reaches the place where needed. 

 The principle which renders starch soluble is an unorganized 

 ferment called " diastase, " which can change two thousand times 

 its own weight of starch into soluble compounds. 



The walls of the innumerable cells of the plant framework are 

 constructed of cellulose, a substance having the same composition 

 as starch. Where growth occurs in the enlarging plant, the newly- 

 formed cells are tender and filled with protoplasm. Each cell 

 divides into two or more cells, the newly-formed members growing 

 to full size. The cell walls thus enlarged are built of soluble 

 sugar changed to insoluble cellulose through the action of pro- 

 toplasm. 



7. Growth from the chemist's standpoint. Let us review the 

 subject of plant growth, as we have studied it to this point, from 

 the position of the chemist, in order to fix more clearly in mind 

 the process of plant growth. 



With the chemist, " O " stands for oxygen, " H " for hydrogen, 

 "C" for carbon. Water is composed of two atoms of hydrogen 

 chemically united with one of oxygen. This molecule, which is 

 the smallest division of the water particle, they symbolize as 

 H 2 O. In the same manner carbonic acid gas is indicated by CO 2 . 



