IN CEYLON. 
43 
Rings of Growth. 
These are inconspicuous in the majority of our species. 
According to Ursprung the timber of some species of 
Diospyros presents well defined rings of growth when the 
trees have been grown under a subtemperate climate. 
The whole of our Ceylon species are characterized by a 
slow rate of cambial activity, and, with the exception of the 
partially deciduous trees of D. montana and D. ovalifolia, 
may be regarded as typical evergreens. Nevertheless, the 
majority of our species are characterized by foliar periodi¬ 
cities which recur, fairly regularly, year by year, and these 
together with the independent effects of a hot dry season, are 
perhaps responsible for the zoned differentiation often met 
with. We have also to allow for the possibility of special 
periods of activity determined by internal forces and 
expressed in the differentiation of irregular patches of xylem. 
In the majority of the specimens examined the inconspicuous 
rings have been difficult to follow throughout the whole of 
any transverse section, many being tangential bands in 
association with a neighbouring branch, and therefore 
roughly limited to the side on which the branch occurred. 
In timber of D. insignis and D. Thwaitesii rings of growth 
are visible to the naked eye, and consist of broad dark bands 
alternating with narrower bands of a lighter colour. The 
narrow light rings vary from 0-2 mm. to 1*2 mm. in radial 
diameter, and are disposed at very varying distances — 
radially—from each other. 
The rings of growth are often present in one part of the 
section and gradually merge into adjacent rings of growth, 
and in consequence of this, and the varying radial distances 
(2 to 8 mm.) between successive rings, we find that the 
number of rings along different radii is subject to great 
variation. It is impossible to at present determine in our 
Ceylon ebonies the exact representation of time of each ring 
of growth. 
