CHAPTEE X 
CAUSES OF DECAY AND DESTRUCTION OF TIMBER 
Decay Caused by Bacteria and Fungi — All Timber Liable to Attack — ■ 
Propagation of Disease — Conditions for Decay — Timber in Certain 
Situations Practically Indestructible — Harder and Denser Woods 
Less Liable to Decay — Animals whicli Destroy Timber in Sea 
Water — The Teredo Navalis — Limnoria Terebrans — Chelura 
Terebrans— The Sphseroma — The Pholas — All Timbers with Few 
Exceptions Liable to Attack — The White Ant. 
The changes which take place in the structure of wood 
and cause decay are due to the activity of the lower 
forms of plant life, bacteria and fungi, chiefly the latter. 
Fungi induce changes in the organic matter of the wood, 
by withdrawing certain substances from it on which they 
feed, and the term " decay of timber " is now understood 
to mean a breaking down of the complex chemical com- 
pounds which it contains into much simpler ones, due to 
the activity of these lower organisms which excrete 
ferments ; these dissolve out certain parts of the walls of 
the cells of the wood and, by so doing, destroy their 
physical and chemical properties. 
The cells which make up the heartwood of a tree con- 
tain no living substance. The sap is the life of the tree, 
and is confined to the outer layers. It is composed of 
water holding in solution various organic substances — 
sugars, starches, oils, etc. — and their presence is the cause 
