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. 



Tbe 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 JX 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 - 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. 



