THE POWER OF SUNLIGHT 103 



The make of the soil is thus of great importance. 

 It may be good or bad for the plant. It may be too 

 dry or too damp. It may be lacking in just that de- 

 scription of food which is necessary for the particular 

 manufacture of that plant. If the soil be good, the 

 plant will be healthy, and will work with vigour; if 

 bad, then the plant must become sickly and feeble. 

 But still in every case each one produces, and can 

 produce, only its own especial materials. 



" Ask me why I send you here 

 This firstling of the infant year; 

 Ask me why I send to you 

 This Primrose all bepearled with dew. 



Ask me why this flower doth show 



So yellow, green, and sickly too ; 



Ask me why the stalk is weak 



And bending, yet it doth not break; 



I must tell you, these discover 



What doubts and fears are in a lover." l 



III PLANT MANUFACTURES 



By far the greater part of this complicated work is 

 carried on by the Green Leaves of plants, though not 

 the whole of it. 



One exception is in the matter of Wood. Our larger 

 trees contain masses of wood. In the trunk is the 

 softer sap-wood, close to the bark, full of tiny channels 

 through which the sap journeys. And also there is 

 the heart-wood, filling up the centre with hardened 

 remains of channels, through which the sap no longer 

 pas.ses; and that part is nearly dry. 



* Thomas Carew (about A,t>. 1600). 



