HOW TREES GROW 13 



a bead, or large as a football, they contain those two necessary 

 elements, a young tree and stored food. From its parent tree 

 the seed has also derived certain structures and the power to 

 grow if conditions are favorable. Thus equipped it is cast forth. 



But conditions, in the world of trees are seldom favorable. 

 Most of these millions of seeds scattered throughout a forest 

 find it impossible even to begin the first processes of growth. 

 Some fall in dry, sun-baked earth, or rocky ground, or on 

 impenetrable mats of grass or beneath dense shade. There they 

 die. But some more fortunate seed may find itself one day in 

 early spring deeply embedded in a patch of moist earth on 

 some sunny hillside. From the soil, water soaks into the seed. 

 It swells and finally bursts its covering. Oxygen diffuses 

 through its tissues and many chemical processes take place 

 with great rapidity. The starchy food stored up in the seed 

 becomes digested. The starch changes to sugar and these sugar 

 solutions attract more water from the outside, thus increasing 

 the swelling. Energy is set free by the action of oxygen on 

 the sugar and promotes growth in many ways, but most of 

 the energy is derived from the seedling's surroundings, much 

 more than by the slow burning of the food stored within it. 

 Soon the delicate first root emerges and elongates into the 

 soil beneath. The materials that go to make up this root are 

 derived from the seed and the soil water. During all this time 

 heat is absorbed from the soil and air. And this heat, together 

 with the energy set free from chemical changes in the seed 

 makes the little seed machine operate just as the energy of 

 burned coal makes a steam engine operate. 



No matter in what direction the root is pointed when it first 

 emerges from the broken seed coat, its tip soon points down- 



