I9 FLOWER-LAND. 



great stores from which the plant builds up its 

 substance. 



But whilst assimilation goes on only under the 

 influence of light, always by day and by night plants 

 are working in another way in connection with the 

 air. They are taking in the oxygen and giving off 

 carbonic acid gas, and this is known by the name of 

 respiration* What a good thing it is that plant- 

 respiration, by which the plants take up that part of 

 the air which we require to live upon and give off 

 that gas upon which we cannot live, is very small 

 compared with plant assimilation, which does the very 

 contrary ; so small that on the whole it is not notice- 

 able, and does not hinder the great and beneficial 

 work which the plants do for us by assimilation. 



So if you have many flowers in your room during 

 the dark hours of night, when no assimilation is going 

 on, but respiration continues, they will help to make 

 the air impure and unhealthy for you. Indeed 

 flowers which are not green (p. 197) do not assimilate 

 at all, but they respire the carbonic acid gas ; and 

 some are particularly injurious, because of other 

 poisons which they give off. 



So now by these changes the liquid food or sap 

 has become much changed from what it was when 

 first absorbed by the roots (crude sap). It has been 

 added to and altered, mainly in the leaves, and as it 



*From the Latin "re," again, and " spiro, " I breathe. To breathe 

 out again, to breathe back. 



