The Structure of a Tree 



the lowest limbs is so much greater than on young 

 trees? Where is the growth in a tree, that causes 

 the trunk to become 

 longer? 



Mark off with ink the 

 first foot of the end of a 

 rapidly growing vine or 

 other shoot into inch 

 spaces. Watch the 

 plant for a number of 

 days. Where do the 

 marks become separated 

 most widely? 



Wood ( Bark 

 Cambium 



FIG. 10. The cambium is a growing layer 



between the wood and the bark. 



How a tree grows in 

 diameter. A tree in- 

 creases in diameter 

 through the growth of 

 the cambium. This is a layer of growing cells just 

 inside the bark. Each year the cells of the cambium 

 multiply ; during the growing season they are constantly 

 being divided by longitudinal partitions which cut off 

 layers of cells on both the inside and outside of the 

 cambium. On trie outside this forms a thin layer 

 of tissues in the inner part of the bark; inside the 

 cambium a new layer of wood is laid down. Thus 

 each year a sheet of wood is laid upon the tree from 

 the outside. This causes the tree to increase in 

 diameter. 



If you could remove from a tree the layer of wood 

 that is added in a single year, what shape would it have ? 

 Do the layers of wood that were formed when the tree 



