THE BLUEING OF CONIFEROUS TIMBER. 83 



disease, and to refer to the work of Dr B. D. Macallum, who 

 has recently worked out the Hfe-history of one of the species 

 concerned — Ceratostomella piceae — in Edinburgh.^ By the 

 courtesy of Professor Hudson Beare I am also enabled to 

 publish the results obtained by him during the late war, while 

 testing the strength of specimens of timber of Scots pine 

 attacked by the disease (cf. p. 71). 



Hartig referred to the "blueing" in his work on the 

 destruction of timber by fungi, and also in his book on the 

 diseases of trees ; he showed that the infected wood contained 

 brown hyphae in its cells, especially in the medullary rays, and 

 that these belonged to Ceratostoma piliferum, Fuchel. Neither he, 

 nor the investigators mentioned below, have been able to explain 

 how the blue colour is produced, for the walls of the cells are 

 not coloured by the contained hyphae. Two suggestions have, 

 however, been put forward in explanation, the first being that 

 the brown colouring matter of the fungus contains a small amount 

 of blue pigment, whose colour is transmitted by the cells more 

 readily than the brown colour ; and the second, that the colora- 

 tion is an entirely physical phenomenon, depending on the 

 distribution of the large number of small hyphae in the wood, 

 and is comparable to the blue colour of the sky produced by 

 the suspended particles in the air. 



The diseased timber has a very characteristic appearance. 

 The whole of the specimens may be affected, but frequently 

 the "blueing" occurs in patches and streaks, and is confined to 

 the sapwood. The actual colour of the wood in the early 

 stages of attack varies from grey to blue or greenish-blue, but 

 later on the colour deepens and the timber may become greyish- 

 black, due at least partly to the formation of numerous fungus 

 fructifications on its surface. During the early stages there 

 is little apparent alteration in the physical condition of the 

 timber, but, if the disease continues to develop, the wood 

 softens and ultimately a certain amount of rotting goes 

 on. 



The disease is chiefly due to certain species of Ceratostomella, 

 previously included under the name C. pilifera, but a number 

 of other fungi are often present. The species of Ceratostomella 

 are characterised by small fructifications, the perithecia, which 



^ An account of this work will shortly be published in the Tratisactions of 

 the British Mycological Society. 



