On the Quantity of Wood-gum (Xylan) contained 
in Different Kinds of Wood, 
BY 
J. Okumura, Nôgakushu 
The durability of wood is of great importance for industrial 
purposes. This durability depends not only upon the greater or 
less density, but also upon the presence of certain chemical cons¬ 
tituents. Thus a certain proportion of resinous matters will 
increase the durability, while the presence of easily soluble 
carbohydrates may diminish it considerably. The durability 
consists in a certain resistance to the attacks of different kinds 
of fungi, as Polyporus , Agaricus, etc. Resinous matters can 
never be attacked by these fungi, but various carbohydrates, 
as starch, wood-gum, and even cellulose are sometimes rapidly 
dissolved by the ferments produced by these fungi which thus 
prepare their way to penetrate into the interior of the wood. 1 * 
From this stand-point it seemed to me to be of great interest to 
determine the amount of wood-gum in a series of trees grown in 
Japan. Of course the quantity of wood-gum will not be found 
always to be a constant figure. The proportion may differ 
somewhat between the heart-wood and bark, and also may vary 
with the age of the tree. It is certainly of physiological interest 
that Thomsen found great differences in the amount of wood-gum 
in sap-wood and heart-wood as seen from the following table :— 
Dried at ioo c C. 
% in dry 
matter. 
Sap-wood. 
Heart-wood . 
Betula alba L. (old) 
* 3-9 
19.7 
,, (young) 
24.9 
26.4 
Fagus sylvatica , L. (ioo years old) 
8.2 
15-9 
>» (young) 
11. g 
ii -3 
Quevcus glandulifera , Bl. 
14.4 
10.7 
Prunus pseudocerasus, L. 
19-3 
15-4 
i) The observations of R. Hartig in this 
direction are of s 
•peciai importance. 
