DRY-ROT OF INCENSE CEDAR. 41 
Besides the trees shown in Table VIII, there were seven on the 
intermediate area and five on the optimum area with slight wounds 
which appeared to have resulted from lightning; but an absolute 
determination was impossible. The meager basis in this table shows 
practically an equal number of lightning-scarred trees in the two 
localities. 
BREAKING BRANCHES. 
Incense cedar does not prune itself easily even when growing in a 
dense stand, a fact attested by the persistence of the lower limbs. 
In time, however, some of the lower branches die and break off. The 
dead stubs then offer a point of entrance for heartwood-destroying 
fungi ; the spores lodging in the dead wood may germinate, develop, 
and the fungous hyphas pass through the bark and sapwood of the 
tree into the heartwood b} r way of the pin knot. The pin knot in 
this case plays exactly the same role as an open wound, but it must 
be remembered that the area for lodgment of a fungous spore on a 
pin knot that is not healed over is exceedingly small in comparison 
with other types of wounds. On the other hand, there are normally 
from several to many open pin knots on each tree, and every tree, 
throughout all but the earliest years of its life, is thus exposed to 
inoculation by fungous spores through these open pin knots. Many 
of course heal over, but others take their places. 
OTHER CAUSES. 
Besides the causes of wounds already discussed, there are a few 
others of minor importance. 
vStrong winds will occasionally break off branches or tops, or over- 
throw entire trees, particularly those weakened by a bad open fire 
scar in the butt. The thick foliage of incense cedar collects a very 
heavy weight of wet snow, often causing the tops and branches of 
young trees especially to break off. Sometimes a falling tree will 
rake off the limbs and part of the bark of a neighbor. Such injuries 
are usually superficial unless very large branches have been broken 
off or the bark has been torn away from the trunk over a considerable 
area, 
Alan is at times directly responsible for certain wounds. It is quite 
a common sight along a newly constructed road to see bark torn off, 
often rather high on the trunk, where the tree has been struck by a 
flying rock from a powder blast. Some wounds result from blazing 
trees to mark a boundary line or trail, but they are usually small and 
rapidly heal over. 
• Broken or dead tops, the cause of which is often impossible to 
determine, are not at all rare. Trees with these injuries comprised 
6.9 per cent of the total number on the intermediate area and 7.1 
per cent on the optimum area. 
