62 OF WOOD IN GENERAL 



Anotlier species of Pol^porits, P. vapordrius, though it acts as a 

 wound-parasite on coniferous trees, frequently develops and does 

 its chief mischief in stacked timber. It is then commonly confused 

 with the true dry rot, of which we shall speak presently. Its 

 spores (which are, as in most fungi, extremely minute and produced 

 in myriads) fall into cracks of wood, whether the result of injuries 

 to timber when standing, or " shakes " developed after the tree 

 is feUed and barked. As their spawn-threads develop in the timber 

 and gradually decompose and absorb its substance, the wood 

 shows deep red or brown streaks, warps and cracks up, and becomes 

 thoroughly rotten, and is penetrated by thick snowy- white ribbons 

 of the felted fungus. In stacked timber this rot frequently develops 

 mainly in the lower, less ventilated, layers of a stack. 



Some of the diseases that show themselves conspicuously in the 

 cortex and are known as cankers may be set up by frost, by sun, 

 or by insect attack ; but in Oak, Beech, Maple, Hornbeam, Alder, 

 Lime, and Larch, canker is mostly the result of wound-parasite 

 fungi. The spores of most, if not all, of these fungi are incapable of 

 penetrating sound cortex; but how many are the chances that 

 bring about small ruptures of this layer ! In the case of that 

 most destructive of cankers, the Larch disease, it has been shown 

 that the fungus which produces it, Peziza WillJcommii, is far less 

 common and less deadly in the drier colder air of Alpine heights 

 where the Larch is indigenous ; but that late frosts attacking the 

 more advanced and sappy trees in the moist air of the lowlands 

 kill many a shoot and form wounds by which the spores can enter. 

 The moister and warmer air at the same time is more favourable 

 to the growth of the fungus. Its spawn-threads ramify in all 

 directions through the wood, turning it brown and drying it up ; 

 while resin flows out at the wound in the bark, which enlarges 

 yearly as the tissues surround it with successively wider-gaping 

 lips of cork in the futile effort of the tree's vitahty to heal it over. 

 Round the margins of the wound appear the httle orange cup- 

 shaped fructifications of the Peziza scattering their spores so as 

 to infect other trees ; whilst the ultimate effect is that each tree is 

 ringed by the destruction of its cortex and then generally succumbs. 



Many of the fungi which attack standing timber are so ruinous 

 in their action that the wood of the affected trees will never reach 

 the hands of the timber-merchant ; but the wood-worker is more 

 seriously interested in those diseases which attack converted 

 timber. Of these the most important is " dry rot " {Memli%$ 

 Idcrymans), The spores of this fungus germinate on damp wood, 

 provided some alkali is present, such as the ammonia fumes in 

 stables. Then, under the influence of warm, still air (i.e, the 



