(UNIVE: 



V 

 ^^t- 



THE LEAF 93 



dark, keep them in strong sunlight out-of-doors. No 

 carbon dioxide should now be found, for, as fast as it is 

 formed by the breathing of the plant, it is used up in 

 the process of assimilation. 



These three experiments teach us that the processes 

 of burning and the breathing of 

 animals and plants agree in result- 

 ing in the formation of carbon 

 dioxide. 



Place some leaves in a wide- 

 mouthed bottle, fill with water, 

 and place it in the sunlight (see 

 Fig. 13). Observe that in a short 

 time small bubbles of gas appear FIG. 13. Experiment to 



,11 ,. , . ,., show the bubbles of gas 



on the leaves which are in reality given off from ]eaves s in 

 bubbles of oxygen, formed in sunlight. 

 the process of assimilation and given off by the plant. 

 On repeating this experiment, but placing the bottle in 

 the dark, no bubbles will be given off, for, under these 

 conditions, no assimilation can go on. 



The Food of Plants. 



Take enough starch just to cover a threepenny-bit, 

 drop it into about half a pint of boiling water, and, when 

 cold, add a little iodine solution. The liquid becomes a 

 deep blue. (If you have too much starch present the 

 colour will be almost black, and water should be added). 

 This is a convenient test whereby to recognise the 

 presence of starch. 



Take a few leaves which have been exposed to bright 

 sunlight for several hours (fuchsias answer admirably), 



