176 LIFE OF A TREE. 
ing them from place to place in the stem, 
Hence, it is not actually necessary that the 
trunk should be perfectly solid, so long as 
enough wood remains entire to perform these 
two functions. The mere fact, therefore, that 
the trunk is hollow and time-eaten, even to a 
very large extent in the centre, is of but little 
consequence to the life of the tree. As it is well 
known that a hollow pillar is stronger than a 
solid one, there is no fear on the score of 
weakness, unless the internal decay proceeds at 
a very rapid rate. And so long as a sufficient 
amount of woody tissue remains in the circum- 
ference to carry on its usual duties, there is 
little fear of the death of the tree. The branches 
with their ten thousand workmen, the leaves, 
are continually condensing fresh wood from the 
very enemy the tree has most to fear—even 
the tempestuous air. Not a wind that howls 
through its boughs, rustling with the quaking 
leaves, but parts with some portion of its 
contents to contribute to the strength and 
endurance of the venerable trunk, with which 
it has so long vainly contested. Not a drop 
of rain that falls in pitiless fury upon its aged 
