4 MISC. PUBLICATION 162, U. S. DEPT. OF AGRICULTURE 
Air supplies carbon. 
the principal food of 
the tree Taken inon 
under surface of 
leaves 
Tree increases each year 'n 
height and spread of branches 
by adding on new growth of 
twigs 
Leaves prepare 
the food obtained 
from airand soil Light and heat 
and give off > necessary for 
CROWN moisture by ,agane fe 
chemical ch 
Transpiration - mica! changes 
Heartwood (inactive) 
gives strength 
Sapwood carries sap 
TRUNK from ip erO Cees The breathing pores of 
the entire tree=-on leaves 
twigs. branches,tninkand 
: roots take in Ox~ygen. 
[ Flooding, poisonous gases. 
orsmoxe may kill a tree 
Cambium (microscopic) 
builds the cells 
Inner bark carries 
prepared food from ; 
leaves to Cambium layers 
Outer bark protects 
tree from injuries 
Surface roots 
- ae = 1 Sy = — 
E Ee J 
eon st Aas pastes 
oe <= = 4 Fy ta 
= ° . p YAWN c 
Root tips or root hairs take 
up water containing small 
Quantity of minerals in 
solution. 
Taproot 7 \\ 
} 
Figure 1.—How a tree grows. 
The buds, root tips, and cambium layer are the growing parts of the tree. Water e 
containing a small quantity of minerals in solution is.absorbed by the roots, 
carried up through the sapwood to the leaves and there combined with carbon 
from the air to make food. This food is carried by the inner bark to all 
growing parts of the tree, even down to the root tips. 
