6 
APPEARANCE AND TEXTURE OF BARK. 
(b) THE BARK. 
The outer bark of Eucalyptus trees, like that of many other genera, tends 
continuously to become sapless and dry. It thus in successive ajms ceases <3 e 
a living part of the tree. In some species this dead bark peels off 1I ‘ llbl ^° s ’ 
scales, or sheets. The process uncovers the living bark and gives to the stems 
and branches of the trees a naked and pale-coloured appearance. Trees with this 
deciduous bark habit are technically called “gums.” In other species the dead 
bark clings to the trees and forms a close fitting jacket over the living bark on 
stems and large branches. Trees with this persistent bark habit are not gums 
and should never be so called. A few species have their tops naked and their 
stems clothed to a greater or less height with persistent dead bark. ^ney are 
said to be “gum-topped” or “half-barked”; but even these are technically not 
“gum trees.” When we speak of certain barks as persistent we do not mean that 
they are free from any kind of change. All organic things change, and those 
barks that persistently cling to the trees are subject to weathering and waste at 
their exposed surfaces. Barks of all descriptions are thus in a state of continuous 
mutation. Living bark grows from the cambium tissue, fulfils certain functions, 
and then becomes dead bark. Dead bark gradually perishes and goes back to the 
earth, either by peeling off or through weathering and wasting at its surface. The 
process is analogous to the birth and life and death of leaves, and more remotely 
to the continual renewal of the skin in animals. 
In the case of every persistent dead bark we have the phenomenon of a close- 
fitting dead coating surrounding a living and growing tree. It is obvious that 
any such coating must become rent, cracked, or fissured by the increase of the 
tree’s diameter. It is obvious also that the manner of the rending or cracking will 
be determined by the peculiar texture of the dead substance. The effect of the 
tree’s expansive force upon the persistent dead bark thus becomes an aid in 
determining the species, and must always be noted in connection with the texture 
of the bark itself. 
Leaving out of account all minor distinctions, persistent dead Eucalyptus 
barks may be grouped as follows:— 
1. Soft barks with long, tough fibres. These are described as fibrous or 
stringy, and are seen in their most characteristic forms on the trees commonly 
called “stringy-barks.” The cracks or rents in these barks run in nearly parallel 
lines up and down the tree. The “blackbutt barks” of Eastern Australia are soft 
and fibrous and form a sub-section of this group. 
2. Soft barks in which the successive layers of fibres cross each other obliquely 
and present, as the tree expands with growth, a reticulated or latticed appearance. 
These barks are found on the trees commonly designated “peppermints” and are 
consequently called “peppermint barks.” The fibres in these barks are at first 
tough, but through expansion and exposure to the weather they ultimately lose 
their tensile strength and can then be easily broken or crushed in the hand. 
3. Soft barks with short, brittle, and irregularly arranged fibres. Some of 
these are coarse and deeply furrowed; others are finely divided, fleece-like, felt¬ 
like, or scaly. These barks are described as sub-fibrous when the fibrous texture is 
