86 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



rays and resin canals, where they live upon the contents of the 

 parenchymatous cells, dissolving the starch grains and destroying 

 the walls, and becoming so abundant as to fill up the entire 

 ray. The older hyphae turn brown, and with the first sign of 

 the brown colour the blue coloration of the wood begins. 

 Apparently the cellulose walls are not decomposed by the 

 fungus, but the hyphae pass into the tracheids from the 

 medullary rays, sometimes penetrating the tangential walls 

 by bore holes but more often passing through the simple or 

 bordered pits. In these cases, it is evident that a certain 

 amount of decomposition of the strongly lignified walls must 

 go on. As a general rule the hyphae do not grow into the 

 heartwood, probably on account of the absence of food 

 materials from this part of the tree. 



Miinch has carried out a large number of experiments to 

 determine under what conditions wood of pines and firs 

 becomes infected by the blue-stain fungi. He found that the 

 various species of Ceratostomella readily developed on the 

 surface of fresh sapwood of trees felled in winter, but that the 

 hyphae only penetrated to a small distance into the timber, 

 and that the latter did not become discoloured. It was only 

 after the timber had lost a considerable percentage of its 

 moisture that it was penetrated by the fungus, and took on the 

 blue coloration. By further experiments he showed that the 

 non-penetration of fresh timber was determined by lack of 

 oxygen, and that after loss of water and the consequent entrance 

 of air the fungus readily grows throughout the wood. The 

 "blueing" is rapidly produced when the timber has lost lo- 

 20 per cent, of its moisture, and even goes on when the wood 

 is in a comparatively dry state. In relatively damp wood the 

 mycelium develops most freely in those parts of the sapwood 

 which are richest in air ; in consequence, the staining is most 

 strongly marked in the portions immediately bordering on the 

 heartwood. He points out that in practice any conditions which 

 preserve the moisture, such as the retention of the bark on 

 felled trees, will tend to prevent the attack not only of Cerato- 

 stomella but also of other wood-destroying fungi, the growth 

 of which is probably inhibited in the same way by the lack of 

 oxygen. The practice of keeping timber in water is one of 

 the best methods of preservation not only against "blueing" 

 but also against the attack of various wood-destroying fungi, 



