72 OUTLINES OF BRITISH I'UNGOI.OGV. 



establish themselves on the previously diseased stems of trees. 

 But though such Fungi do not attaek healthy trees, their 

 spa^vn soon spreads, and speedily destroys the surrounding 

 healthy tissues. The evil can be stopped only by carefully 

 cutting out the diseased parts, and washing them witli a 

 strong solution of corrosive sublimate, or other substance 

 which may destroy the spawn without injury to the tree. 



Of those which attack timber when converted to the pur- 

 poses of marine and domestic building, the most formidable, 

 perhaps, is Dry-rot (Plate 2, fig. 1), which derives its name 

 from converting the wood into a dry powdery mass, though 

 both the Fungus and wood are often sprinkled with large 

 drops of moisture. This may, however, be prevented by pre- 

 viously impregnating the pores of the wood with gas-tar, sul- 

 phate of copper, or some other poisonous metallic salt ; or, 

 when established, may be greatly modified by careful, and, if 

 needful, repeated washing w'ith a saturated solution of corro- 

 sive sublimate. This treatment may not destroy the whole of 

 the spawn, but if not, it will at least greatly diminish its ve- 

 getative power. 



It is still a question amongst shipbuilders, whether winter 

 or summer felled timber is most subject to be afiected. It is 

 quite certain that, in dry situations, timber felled when the 

 trunk is most free from sap, is far more durable. There are 

 many ancient buildings in which the sapw ood is still as free 

 from insects and decay as the firmest heartwood; but where 

 there is not a free current of air, and Fungi can establish 

 themselves, the mischief is so inherent in either case that it is 

 only a question of time. In domestic buildings, where little 

 choice is exercised in the selection of timber so long as it be 

 of the proper size, and it has not to undergo the scrutinizing 

 eye of a dockyard surveyor, the wood is often deeply impreg- 



