596 QUEENSLAND AGRICULTURAL JOURNAL. [1 Dec., 1899. 
Cellulose.—The primary constituent of the cell wall in the young and 
growing plant is cellulose, a substance which is to be had in a nearly pure form 
in cotton and unsized paper. It has the formula (C, H,,0,), and contains 
carbon 44°44 per cent., hydrogen 6°17 per cent., and oxygen 39°39 per cent. It 
is very inert to all ordinary decomposing agents, such as air and moisture, but 
is acted on by certain re-agents, yielding products which are of commercial 
importance. 
When cellulose is treated with sulphuric acid it is converted into an 
amorphous mass known as amyloid. Advantage is taken of this reaction in the 
manufacture of parchment paper, which is paper which has been partially 
converted into amyloid by the action of sulphuric acid. 
When cellulose is treated with a mixture of nitrie and sulphuric acids it 
gives rise to nitro-substitution products, the most important of which C,, H ,, 
(NO,) ,O,¢, is called pyroxyline or gun cotton, and is a powerful explosive. 
Nitro-cellulose treated with camphor yields the substance celluloid, which is so 
largely used for the manufacture of small articles. 
Treated with an ammoniacal solution of copper oxide the cellulose is 
dissolved, and is reprecipitated from the solution on addition of acid. When 
such a solution is evaporated it leaves a gummy mixture of copper, oxide, and 
cellulose. Willesden water-proof paper is prepared by passing paper through 
the ammoniacal solution and then drying it. The amorphous layer of copper, 
oxide, and cellulose left on the surface is perfectly water-proof. 
Composition of Wood.—As the growing cells become differentiated into the 
wood cells, and the walls become thickened, the cellulose undergoes very great 
changes. On the outer side of the cambium layer various complex adipo- 
celluloses are formed, and on the inner side various ligno-celluloses. Ordinary 
woody tissue is largely made up of ligno-cellulose—a mixture of cellulose and 
lignine. Lignine has the composition C,, H,, O,,, and contains, therefore, 
55°5 per cent. of carbon, and it is comparatively richer in hydrogen than 
cellulose. In addition, the cells contain, intermixed with the cellulose and 
lignine, small quantities of complex bodies containing nitrogen. The cells 
themselves may contain starch and other materials stored up by the plant for 
its future use, and the vessels may contain resins and other complex bodies. 
Wood, therefore, cannot be regarded as being a definite substance, but 
rather as being a mixture of substances, some of which are much less stable, 
and are more readily attacked by organisms and inorganic re-agents than others, 
The average composition of dry wood is about—Carbon, 50 per cent, ; 
hydrogen, 6 per cent.; oxygen, 41 per cent.; nitrogen, 1 per cent.; and ash 
(mineral matter), 2 per cent. ; but all the constituents vary somewhat according 
to the nature, age, &ec., of the wood. : 
Seasoning of Timber.—Wood, as has been mentioned above, is always 
seasoned before use. The object of the seasoning is to get rid of as much 
water as possible, and thus to reduce the weight and to dry up the more easily 
decomposable matters in the sap. Air seasoning is generally used. The wood 
is then stacked so as to be protected from sun and rain, and so as to be freely 
exposed to the air on all sides—a free circulation of air being one of the chief 
essentials of good seasoning. Air seasoning may occupy from two to four years. 
In water seasoning the wood is kept under water for some time. In hot-air 
seasoning the wood is exposed to air artificially warmed to a temperature of 
from 100 degrees Fahr. to 250 degrees Fahr. Various other methods of 
seasoning are used occasionally. 
Varieties of Wood.—Many woods are used for constructive purposes, and 
they vary very much in character and properties. Some are used on account of 
their strength, others on account of their colour or the grain which they show 
on the cut surface, and others for other characteristics. 
The only classification of woods that need be mentioned here is their division 
into soft and hard. The soft woods are chiefly derived from the coniferous trees, 
and contain various resins, though the birch, which yields a soft wood, is not a 
conifer. All the other timber”trees yield hard woods. The hard woods are 
usually more durable than the soft woods. 
