90 THE GARDEN OF EARTH 



plant works thus only in daylight. The breathing of a 

 plant goes on, as with us, both by day and by night. 

 The digesting takes place only while it is light. After 

 dark, it stops. The tree then just breathes as we do; 

 keeping the oxygen of the air for its own use, and getting 

 rid of the carbonic-acid gas. 



And so soon as morning light returns, they are once 

 more at their useful work; and while they still breathe 

 out carbonic-acid gas, they catch it up again as it leaves 

 the little pores, and use it anew as food for the plant 

 to which they belong. 



You would never guess what accumulations of 

 that important but suffocating gas are being manu- 

 factured, day and night, through breathing. Putting 

 aside what plants and animals do, and reckoning only 

 what is done by men and women and children throughout 

 the world, it is said that each day more than one million 

 tons of carbonic-acid gas are poured into the atmosphere. 



So no wonder the daylight task of plants is needed, 

 to undo the mischief which we ourselves are perpetually 

 working. 



" Small service is true service while it lasts; 



Of humblest friends, bright creature, scorn not one. 

 The Daisy by the shadow that it casts 



Protects the lingering dewdrop from the sun." * 



Something has already been said about a tree having 

 to transpire. This really is a kind of perspiration. 



When a man perspires, drops of water are seen on 



his face ; water that has oozed out through tiny pores 



in his skin. When a plant " transpires " the water 



escapes through its skin-pores, as invisible vapour. But 



1 Wordsworth. 



