CRAIB—REGIONAL SPREAD OF MOISTURE IN Woop OF TREES. 15 
Explanation of Coloured Plates (CL-CLIV). 
These coloured plates, it must be borne in mind, are purely 
diagrammatic. The colour scheme adopted, a copy of which 
is found below each diagram, is as follows :— 
Moisture content under 60 per cent. of the dry weight of the 
wood—blue. 
Moisture content from 61-80 per cent. of the dry weight of 
the wood—yellow. 
Moisture content from 81-100 per cent. of the dry weight 
of the wood—grey to black. 
Moisture content over 100 per cent. of the dry weight of 
the wood—red. 
By the use of different shades of these four colours a nearer 
approximation to the actual moisture percentage can be shown ; 
in all four colours the deeper shading indicates a higher per- 
centage, the lighter shading a lower. 
Soon after leaf-fall (in October) the average moisture distri- 
bution, as seen in a transverse section from about the middle 
of the bole, is as shown in Plate CL. From the colour scheme 
it is readily seen that by far the larger portion of the section 
has a moisture percentage of 61-80, as indicated by the large 
area coloured yellow. The youngest wood—on the extreme 
outside—has a percentage of almost 80, and the moisture dimin- 
ishes from this zone to its minimum for the whole section. 
This minimum occurs at about 5 mm. from the outside of the 
plate, as indicated by the blue circle denoting a moisture 
percentage of just under 60. Inside, this minimum there is a 
gradual rise towards the centre, as shown by the more intense 
yellow, until near the centre, where there is a sudden rise from 
81 to 100 per cent. (grey to black), which again is continued to 
‘well over 100 per cent. in the very centre (red). 
In December (Plate CLI—which represents likewise the 
average moisture distribution in a transverse plane at about 
the middle of the bole) shades of yellow, indicating a percentage 
of 61-80, still predominate in the whole section. The very 
youngest wood—on the extreme outside—has here a slightly 
lower percentage than is found in October, and the percentage 
decreases inwards to about the same minimum region—about 
5 mm. from the outside of the plate,—as noted in the previous 
plate. Near the centre we find the same steep rise to well over 
y and black succeeded by red), but the area over 
d) is now considerably larger than in October ; 
t will be noticed that within this red area the 
