394 
Groom.— Brown Oak 9 and its Origin . 
afforded at Radlett by a tree, whose brown wood at the base of the trunk 
extended (apparently) completely across the heart-wood, then tapered very 
sharply in an upward direction, becoming at the same time confined to one 
side of the trunk, and continuing thus upwards, gradually tapering to 
extinction at an approximate height of 15 feet 
In connexion with this partially unilateral arrangement may be 
mentioned the interesting case of an oak-tree that grew near a stream. 
The bole, only 18 inches in height, gave way to two erect stems, each 
of which was about 18 inches in thickness over a length of 12-15 feet 
The stumpy bole showed ‘brown oak 5 on one side only, and the erect 
leader topping that side also was characterized by ‘ brown ’ wood, whereas 
the other leader springing from the half of the bole possessing normal heart- 
wood contained no ‘ brown oak \ 
This case leads to the consideration of those pollard oaks in which the 
main trunk includes ‘brown oak’ extending up to the region of inser¬ 
tion of the branches, which form the multiple leaders of the crown. In tfie 
majority of cases ‘brown oak’ is contained by only one or, perhaps, two of 
the several leaders, and these are inserted above that section of the main 
trunk which is characterized by the strongest and richest colour in its brown 
heart; in such cases the remaining leaders show heart-wood normal in 
colour. Yet occasionally all the leaders (five in one case) include rich 
‘ brown oak 
‘ Brown oak ’ extending upwards in the trunk is usually arrested by 
extensive knots, and, in any case, a large knot acts as an obstacle. Conse¬ 
quently, in such cases, large boughs springing from the side of the trunk are 
apt to be devoid of 4 brown oak ’. The reason for this will be at least partly 
evident, when the cause of the browning of the heart-wood is explained later 
in this paper. 
When ‘ brown oak 5 occurs at the base of the trunk it also extends 
downwards into the main root, where it tapers in the same manner as in the 
trunk. 
Apparently ‘ brown oak ’ may occur in upper parts, including the crown, 
of a tree whose more basal parts are devoid of it. Very significant in 
relation to the cause is Mr. A. Howard’s statement as follows: * it appears 
probable that in a few cases the brown wood may start from a large knot 
below the crown, and extend somewhat downwards’. Mr. Stuart Oliver 
mentions one case in which the brown wood extended completely across 
the heart at the base of the bole, and upwards for some distance, 
then disappeared, only to recur at a height of 35 feet where the bole 
forked. 
Age of trees possessing ‘ brown oak \ While on the one hand very old 
oak-trees contain ‘brown oak’, the minimum age at which the tree can 
acquire it is apparently determined by that at which the heart-wood 
