88 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



Since species of Ceratostomella can attack the living cells in 

 freshly cut pieces of timber, the question arises as to whether, 

 under certain circumstances, living trees may not be attacked 

 and killed by the fungus. Aliinch suggests that the high 

 percentage of water, and consequently the low oxygen-content 

 of the tissues, will prevent penetration by the hyphae, and that 

 normal trees therefore will not become infected. If, however, 

 the oxygen present in the wood is increased by diminishing 

 the water-content, there appears to be no reason why infection 

 should not take place. In order to bring about this condition 

 some of the roots of a tree were chopped through and, in 

 another specimen, the bark and sapwood were sawed through 

 half-way round the stem at two levels, one about i8 inches 

 above the other, so that the wood between the two cuts was 

 completely isolated from its water-supply. Infections were 

 made on the two specimens, and in the first some " blueing " 

 resulted in the older sapwood, while in the second the whole of 

 the wood between the cuts was infected. 



A tree in which the roots have been loosened or broken by 

 a storm, will usually remain living for a considerable period, 

 but may become infected at the base by Ceratostomella and 

 die within a short time. In such a tree partial defoliation will 

 result from the root damage, and the transpiration stream will 

 be thereby lessened; this will gradually lead to a diminution 

 of the moisture present in the sapwood and a consequent 

 increased oxygen-content. Infection in such a case appears 

 to be often brought about by bark-boring beetles, and when this 

 happens the " blueing " fungus is enabled to spread rapidly 

 in the sapwood owing to its increased air-content, and ultimately 

 the tree dies. Death, in such a case, is brought about by a 

 combination of factors, and it is extremely difficult to estimate 

 the relative importance of any one of them. Von Schrenk, in 

 the United States, has described cases in which the attack of 

 bark-boring beetles was associated with the production of 

 " blued" timber. In trees of Finns ponderosa severely attacked 

 by the beetle Dendrocto7iiis ponderosae, the blue coloration 

 of the wood seemed to spread from the beetle holes, and it is 

 suggested that the latter form channels for the passage of the 

 hyphae into the deeper layers of the sapwood. In this country, 

 Dr Macallum, in the paper already referred to, has noted 

 somewhat similar cases. In these the sapwood of dead but 



