INJURIES INDUCED BY PLANTS 219 



was found to be of exceptionally high quality, and showed 

 no blemishes. This was the case even after the barked trees 

 had been piled for a whole year before being removed from the 

 forest. Owing to the stores of carbo-hydrates having been 

 nearly all used up by the cambium in the formation of the wood- 

 ring during the summer of the first year, such timber offered less 

 suitable conditions for the growth of fungi than the wocd of 

 trees that had not been defoliated. It was only after the 

 cortex had died, or had been perforated by wood and bark 

 beetles, that fungi could gain an entrance, when the high 

 temperature and abundance of moisture offered favourable 

 conditions for their growth. The low repute in which timber 

 furnished by trees destroyed by insects is held is entirely due 

 to the fact that such trees are often left standing in the forest 

 till the cortex is dead. Trees that have been stripped of their 

 leaves should therefore be felled and barked not later than the 

 beginning of July of the year succeeding the defoliation. 



I now return to the consideration of the true dry-rot fungus, 

 Merulius lacrymans. 



Although this plant has been encountered at least once on the 

 old stool of a conifer in the open forest, it is usually associated 

 with man. It is probable, however, that it has hitherto escaped 

 notice in plantations, and that it is more generally distributed 

 than is usually supposed. Although it lives chiefly on coniferous 

 timber, it also grows on oak, and the oaken boards of parquet 

 floors are liable to be infected. 



The filamentous mycelium which is invisible to the naked eye 

 grows inside the wood, from which it abstracts the proteids 

 necessary for its growth. At the same time it dissolves 

 the coniferin and cellulose of the cell-walls, and leaves behind 

 a brown residue consisting of lignin, tannin, and oxalate of lime. 

 So long as sufficient moisture is present these substances 

 enable the wood to retain its original volume, but whenever 

 water is withdrawn the wood becomes traversed by numerous 

 fissures running at right angles to each other, and frequently 

 breaks up into regular cubes. 



As the wood decomposes it becomes brown in colour, a result 

 which is probably due to the higher oxidation of the tannin. 

 Although soft when damp, the wood bears some resemblance to 



