282 GLIMPSES IXTO PLANT-LIFE 



The second function, assimilation, depends upon 

 several processes that together go to make up the 

 work of digestion and preparing plant food. These 

 processes are transpiration, respiration, and evo- 

 lution of oxygen ; the latter process is associated 

 with the feeding of the leaf — that is, the absorption 

 of carbon-dioxide. This compound gas is under 

 the influence of sunlight, and by the agency of 

 the green colouring granules, decomposed into 

 carbon-monoxide and oxygen ; the latter is 

 eliminated, whilst the carbon and a part of the 

 oxygen is retained, and with the absorbed water 

 is conx'ertcd into material that the plant can use 

 for the purpose of increasing its structure. 



By a very simple experiment we can prove the 

 escape of oxygen from the foliage of plants. A few 

 spra}-s of such leaves as laurustinus, bay, arbor 

 vitre, and maiden-hair fern should be tied firmly 

 to a piece of stone. We should have ready a 

 soup-plate, a glass shade, and a tub full of fresh 

 spring water (one large enough to allow the shade 

 to be held upright under the water). When all is 

 ready, place the bunch of leaves and stone in the 

 glass shade held horizontalU', and graduall}- sink 



