52 
THE GARDEN OF THE WORLD 
is too big for the bark. The bark stretches and 
stretches and finally cracks. That is why bark 
is so rough and has such deep furrows. 
As the summer comes to an end, the cam¬ 
bium, or growing part, grows more and more 
slowly, and when cold weather comes it stops 
altogether. This slowing up is easily seen at 
the outer edge of the ring as the wood has a 
different appearance. It is that which shows 
clearly the end of one year’s growth and the 
beginning of the next. The ring of wood 
formed during a favorable season—that is, a 
spring and summer with plenty of rain and 
sunshine—is wide. If the season was too dry, 
the ring is narrow. Just as each summer is 
different from the last one, so each ring differs 
from every other. Men who have had a great 
deal of experience in examining annual rings 
can tell what kind of weather there was during 
a certain year by looking at the rings. This is 
very useful when studying extremely old trees 
such as the big trees of California. These trees 
are so very old that they were growing before 
