WwooD 59 
By examining the end of a log we can learn a great 
deal of the life of the tree. It is made up of a number 
of irregular rings and of lines 
radiating from the center and 
running in nearly straight lines 
toward the bark. 
The number of rings tells us 
the age of the tree, as a new 
ring is added each year. 
As the tree grows, the old 
wood near the center becomes eee 
compressed and dry and is Annual Rings and Medul- 
known as the heartwood, while faty Bays 
that portion between the heartwood and bark is called 
sapwood. 
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In some woods the dif- 
ference between the 
heartwood and sapwood 
is very marked. In 
ebony, for instance, the 
heartwood is coal black 
YH and the sapwood white. 
Fie. 78. Log cut lengthwise, showing The sketch shows half 
how ‘‘ Grain’ is formed 
a log, the annual rings 
being indicated, and also the radial lines, called medul- 
lary rays. 
