70 IMPORTANT TIMBER TREES 



The Stomata must have Light. "We have already seen 

 that the stomata, the little pores in the skin of the leaf, 

 literally serve as mouths to take in air a portion of 

 which is consumed as food and reject what is not suit- 

 able, and that they also permit the escape of the surplus 

 sap that comes to the leaves from the roots. But all this is 

 neither so wonderful nor so important as the further fact 

 that they must have light in which to do their work. They 

 close in the absence of light and open only as light is given 

 them. At first thought this feature will appear of little 

 moment, but, when fully understood, it will be seen that it 

 has a controlling influence in the production of merchant- 

 able lumber. When trees are grown in the open, ample 

 light comes to all their branches, or, at least, to their ex- 

 tremities ; but when crowded and the leaves on their limbs 

 are deprived of light, those so deprived are literally starved 

 to death, for the stomata are closed and no carbon can 

 mingle with the mineral ingredients to form food, nor can 

 the poisonous oxygen be exhaled. The result is that the 

 limbs that are deprived of light are not only starved but 

 actually smothered ; and consequently die, decay, and drop 

 off, leaving a smooth stem free from limbs and knots, from 

 which first-class lumber can be cut. 



A tree grown in the open, where neither roots nor 

 branches are crowded in any way, will naturally throw out 

 limbs soon after emerging from the ground, and these will 

 grow until deprived of light by limbs springing out above 

 and reaching beyond them. A struggle for light is then 

 begun and each limb naturally seeks to obtain it and con- 

 sequently lengthens; but the small branches, which in the 

 early life of the limb had light, are more or less deprived 

 of it and die, with the result that the foliage of the tree is 

 mainly on the outer ends of the limbs, which are frequently 

 long and large. Such trees yield but little lumber, for the 

 wood is largely in the limbs instead of in the body of the 

 tree, and what it does yield is of little value, for it is filled 

 with larjje knots. 



