IN CEYLON. 
37 
forest the xylem is characterized by large radial strands, 
0*09 mm. in tangential width, of very large parenchyma. 
These often commence at the pith and run inwards for a 
distance of several millimetres ; they die out gradually^ but 
frequently at the pointed end another radial patch commences 
and extends a considerable distance into the younger 
secondary xylem. 
Similar strands occur in D. Gardneri from Peradeniya, the 
component cells being about twice the size of ordinary 
parenchyma and surrounded by fibres or flanked by a 
medullary ray. When more than one cell broad the cells are 
usually irregularly disposed, occasionally they exhibit a 
radial arrangement, though in no cases do the components 
exhibit the radial regularity of other elements of the 
secondary xylem. 
The cells are parenchymatous with transverse dimensions 
often equal to those of the neighbouring vessels ; they 
possess thin walls, and their contents include starch and 
oxalate of lime. These strands may be purely pathological, or 
they may perform some part in the physiology of a secondary 
xylem of such slow rate of growth. They cannot be 
regarded as parenchyma drawn from the peri medullary 
zone, because they appear in the sapwood of old trees ; their 
presence in radial groups suggests an origin from the 
cambium similar to the broad medullary rays, and accepting 
this as the interpretation one must regard the final irregular 
disposition of the component cells as a consequence of 
active growth evidenced in their abnormal dimensions and 
numerous contents. 
The Percentage Composition of the Secondary 
MyBem. 
These calculations have been arrived at by examination 
of transverse sections of the secondary xylem of young 
twigs and the sapwood of old trees. The number of 
elements of each type within a fixed field of view have been 
counted, and after several areas have been so examined for 
