THE BLUEING OF CONIFEROUS TIMBER. 89 



Still Standing trees of Pinus sylvestris was found to be badly 

 attacked by Ceratostomella pint and C. piceae, and in all observed 

 cases the bark of the trees was riddled by holes made by the 

 pine beetle Hylesiniis piniperda, 



Miinch has suggested that partial defoliation by caterpillars 

 may bring about a predisposing condition for attack by 

 CeratosfomeHa. Such defoliation will diminish the food supply 

 of the roots and lessen their activity in water absorption, and 

 ultimately lead to increased aeration of the wood as already 

 explained, whereby penetration by the hyphae is rendered 

 possible. 



The changes brought about in timber by Ceratostomella can 

 hardly be described as decay, since for the most part the cell 

 contents are attacked and not the cell walls. Although no 

 experimental results are available, it seems orobable that the 

 ** blued " is more liable to decay than the healthy timber. 

 Miinch, however, suggests that the "blued" timber will be 

 less open to attack by wood-destroying fungi, since the greater 

 part of the food material stored in the cells has already been 

 removed by the Ceratostomella. 



A considerable amount of work has been carried out to 

 determine the effect of the " blueing " upon the mechanical 

 properties of the timber. Rudeloff ^ concluded that the infected 

 timber had a slightly greater compressive strength than sound 

 material, but as the water-content of the test pieces was not 

 determined the results are not reliable. Von Schrenk, who also 

 made a number of tests in the United States, found that the 

 "blued" timber was slightly stronger both when compressed 

 endwise and when broken crosswise. But as the "blue" was 

 slightly drier than the sound wood, this investigator concluded 

 that for all practical purposes "blue" wood is as strong as the 

 healthy timber. 



Miinch has carried out a large number of tests on Scots pine 

 timber at Munich, using for comparison perfectly dry samples 

 taken from closely adjoining positions in the trunk of the tree, 

 infecting some pieces with cultures of Ceratostomella pint and 

 allowing the fungus to grow for six months. The importance 

 of determining the exact positions from which samples are 

 obtained will be appreciated, when it is remembered that the 



^ " Untersuchungen uber den Einfluss des Blauwerdens auf die Festigkeit 

 von Kiefernholz,'' Mittlg. aus. d. Kgl. techn. Versuchsanst, 1S97. 



