CATALOGUE OF THE TIMBERS OF THE WORLD 185 



secondary trunks growing out of the butt, all of which were of a very rich 

 brown colour. (After the tree was sold, a man was idly pulling out the 

 decayed wood from a hollow in the side of the trunk when he felt some- 

 thing hard, which he discovered was a small coin, afterwards found 

 to be of Roman origin.) Much more often, however, in the case of 

 pollarded trees, only one or possibly two of the secondary trunks carry 

 brown colour through, and in most of these cases it is noticeable that the 

 secondary trunk or trunks which are affected occur on that side of the 

 main trunk which has displayed the stronger and richer colour. 



In considering the origin of this wood it must be emphasised that 

 " brown oak " is the product of the ordinary species of British oaks 

 (presumably Q. pedunculata and Q. sessiliflora). The cause of the 

 phenomenon was unknown until recently, when it was investigated by 

 Professor Percy Groom. ^ The following are the results obtained. The 

 heart-wood is laid down as perfectly normal heart-wood, which is sub- 

 sequently converted by the action of a particular kind of fungus into 

 brown oak. The scientific name of the fungus is not absolutely estab- 

 lished, though in aU of three specimens, coming from different parts of 

 Great Britain, it was one and the same in species. The fungus causes 

 the wood to assume first a yellow colour, then a richer brown, culminating 

 in a deep reddish-brown or sometimes blackish-brown. It advances most 

 rapidly along the grain of the wood, often at first being distributed along 

 certain strands of the wood and causing these to assume a colour darker 

 than that of the remainder. This usually temporary condition explains 

 the origin of the tortoise-shell variety. The fungus advances more 

 slowly along the medullary rays. These two methods of progression 

 explain how the wood may become thoroughly infected by the fungus, 

 which, however, grows very slowly and incompletely in a tangential 

 direction. Artificial infections of boards or ordinary heart-wood of the 

 oak led to the artificial production of brown oak. The fungus is of a 

 somewhat exceptional type among wood-inhabiting fungi, for it shows 

 only the feeblest power of attacking the actual wood substance ; while 

 it is converting ordinary heart-wood into brown oak, it feeds on other 

 substances in the wood (probably tannin among others). This fact is 

 of importance in appraising the connection between the fungus and the 

 decay exhibited in certain brown oak trees. 



It is widely known that " brown oak " trees when standing sometimes 

 undergo decay. I have observed many cases in which the trunks of oak 

 trees showed the butt in a complete condition of white-rot up to the 

 height of from 3 to 6 feet, but above this the heart- wood was firm, hard 

 brown oak. This was specially noticeable with some fine butts which 



^ Percy Groom, " ' Brown Oak ' and its Origin," Annals of Botany, 1919, 

 vol. xxix. pp. 393-408. 



