90 THE VITAL FUNCTION'S 



ture of chrysanthemum (or other suitable) buds in a vacuum 

 (thermos) fiask. Here the evolution of heat is " cumulative " 

 for a time because the heat cannot escape, and the risiiig 

 temperature accelerates the process of respiration. i 



B. Localisation of Growth in Plants. Response to 

 Stimulus. 



(i) Take two beans which have germinated and produced 

 roots from one to two inches long. If the surface of the root is 

 wet, dry it carefully with a piece of torn filter paper, taking great 

 care not to break or injure the root. With a carefully sharpened 

 stick (or lead pencil) dipped in Indian ink make marks on the 

 root at intervals of one-tenth of an inch from the top to the seed. 

 Now push a large pin carefully through each bean, and fasten 

 to the under side of the cork of a wide-mouthed bottle, so that 

 when the cork is replaced the root of one points vertically down- 

 wards while that of the other is horizontal. Pour a little water 

 into the bottom of the bottle, replace the cork with the beans 

 pinned to it and turn the bottle upside down for a few seconds, 

 so as to wet the beans and provide water for their growth. Leave 

 the bottles till next time. 



(2) Examine the demonstration showing the aggregation of 

 the green motile unicellular plants (Euglena) on the glass side of 

 a jar. The Euglenae were scattered through the water in the 

 jar, which was covered with black paper. The only light reaching 

 the Euglenae came through the stencil holes in the paper, and 

 they moved towards it, eventually adhering to the glass under 

 the openings. 



C. Organic Foodstuffs of Plants and Some of their 

 Colour Reactions. 



Representatives of the three great classes of organic food- 

 stuffs — -proteins, carbohydrates and fats — are stored in seeds and 

 other storage organs such as tubers, and are used to feed the 

 young plant arising from the seed or tuber before it is able to 

 feed itself. These foodstuffs can be identified under the micro- 

 scope, partly by their appearance, partly by the use of different 

 stains and reagents : — 



(i) With watery solution of iodine in potassium iodide 

 (commonly called " iodine solution ") grains of proteins 

 turn yellow or yellow brown, starch blue, cellulose 

 and fats remain uncoloured. 



