THE VERTICAL GROWTH OF TREES. 383 
In the case of the Wattle (Acacia decurrens), no increase 
was found in the first five feet in one year and four months, 
although the whole stem grew from about 7 to 16 feet in 
that period. The Hucalyptus parvifolia example shows 
that a length of 7 feet remained stationary for three years 
and seven months, and at the end of six years only showed 
change of + inch, and this difference probably arose owing 
to the difficulty of measuring along a bent stem. 
Mr. Walker’s example suggests a rate of growth of 
slightly over an inch in one year, but nothing approaching 
this rate has been found in the present tests. In the case 
quoted by Mr. Fowler, the rate of increase for a length of 
nineteen feet was just over half an inch per annum, but 
even this is more than has been disclosed by the foregoing 
tests. At the same time the tree selected for a twenty- 
foot beam would probably be a tall-growing species of 
Kucalyptus, and I have had no opportunity of testing such 
a tree. H. parvifolia only grows to a height of about 
thirty feet. 
In regard to the second question as to the long clean 
boles of many Hucalyptus trees, the explanation lies in the 
fact that where trees grow in warm Sheltered situations 
and are closely packed among many neighbours, they run 
up rapidly in their upward search for the light, and during 
this process the young boles produce many branches which 
never mature, but, at first, when little more than twigs, 
wither and fall. As the tree grows, the limbs attain a 
larger size, but many eventually fall and the trunk becomes 
naturally disbranched, sometimes up to a great height. 
Should a tree grow in the open it will retain a much greater 
number of branches and reach only a lesser height than if 
it had grown under sheltered conditions. 
Some evidence in regard to the loss of branches may be 
found by reference to the table illustrating the growth of 
