IN CEYLON. 
47 
attained the standard dimensions, and at such a rate that 
only one-fortieth to one-sixtieth of the forest acreage under 
his charge is cleared each year. 
The occurrence of ebony within the plant cannot be 
stated in terms of the age of the tree, the dimensions of the 
stem, or the climatic conditions under which the plants 
have been grown, though a few facts capable of a very 
general application may be here given. The black heart- 
wood occurs usually in the stem, but is often present in 
young twigs and roots. In the majority of our species the 
discolouration commences in the perimedullary zone and 
spreads from within outwards. The discolouration is usually 
of an uniform black in D. Ebenum, streaked in D. oocarpa, 
D. afïinis, D. quæsita and others, red in D. Moonii, and a 
dirty white in such species as D. insignis and D. attenuata. 
The discolouration may occur in the oldest central wood 
only, or it may appear in local strands throughout the 
secondary xylem of the stem. In many young stems the 
only areas where ebony has been produced are directly 
associated with insect punctures, wounds, &c. 
The occurrence of the central black wood within the 
length of the stem is often erratic, though most usually it 
decreases in volume from below upwards. 
The eccentric formation is where the central column of 
black wood widens and narrows repeatedly at different points 
along the stem, and in consequence of this one cannot 
accurately estimate the volume of ebony in a stem by 
external observations alone. In some instances, particularly 
in young stems and twigs, the black heartwood repeatedly 
dies away and reappears at different points along a given 
length. 
The age of a particular tree or the dimensions it has 
attained do not afford a sure criterion as to the quantity of 
ebony it will possess, though the probabilities are that the 
older the tree and the larger the dimensions, the greater 
will be the proportion of discoloured heartwood. This 
