66 



TREE TRUNK 



wood, and lines the old bark with a new layer of bark. The 

 wood that grows in the spring is lighter in color and softer 

 than that grown later in the season. So each year's growth 



makes a double ring, a 

 thick, light-colored part 

 and a thinner and darker 

 part. By counting the 

 rings you can tell the age 

 of the tree. 



Which part of the 

 wood has the larger pores, 

 that grown early or that 

 grown late in the season ? 

 When the inner part 

 of the ring of bark grows 

 larger, what happens to 

 the outer part? Why 

 is old bark rough and 

 cracked on its outside? 

 Why is bark on young 

 branches smoother than 

 bark on older ones ? 



Where Sap flows in a 

 Tree. Sap is the blood 

 of a tree and contains 

 everything that changes 

 into wood, leaves, and 

 bark. From the soil 

 through the roots the 

 plant gets some of its 



APPLE TWIGS SPLIT TO SHOW COURSE OF SAP water > and also its ashes > 



or what is left after wood 



is burned. From the air, through the leaves, the- sap gets its 

 charcoal or carbon. When wood is burned, the most of the 

 carbon passes back to the air. 



