Dischidia rafflesiana ( Wall .). 251 
outer, as within the same distance of the inner surface. On 
the outer surface the laticiferous tubes often approach very- 
near to the stomata ; on the inner surface, though the stomata 
are more numerous, this rarely occurs. The distribution of 
the laticiferous tissue may possibly indicate a relation to the 
assimilating system, but other explanations are not excluded. 
We will next consider the epidermis of the two organs. In 
the leaf the cuticle is of the same thickness on both surfaces, 
in the pitcher ; it is, as one would expect, thicker on the outer 
than on the inner surface. As regards the number of stomata, 
the outer and inner surfaces of the pitcher present a marked 
difference, which is entirely wanting if we compare the corre- 
sponding sides of the leaf. 
In the case of the leaf, the number of stomata on the upper 
and under surface was found to be the same, being as nearly 
as possible 26 per sq. mm. for each, taking the mean of 43 
numerations. 
In the pitchers of the specimen from Java the average 
number on the outer surface was 16-5 per sq. mm. (mean of 
38 countings) and on the inner surface, 33-5 (mean of 39 
countings). 
In some pitchers of D. rafflesiana sent to Kew from the 
Shan states of Burmah the difference was still more marked, 
the numbers being: outer surface 217 per sq. mm.; inner 
surface 57-2 per sq. mm. (mean of 15 countings in each case). 
We see then that the inner surface of the pitcher is charac- 
terized by its structure as the transpiring surface par excellence 
of the plant, this being indicated both by the presence of 
spongy parenchyma in this region only, and by the relatively 
large number of its stomata. 
On the outer surface of the older pitchers we occasionally 
observed patches of periderm, developed under the stomata. 
In these cases the stomata were sometimes replaced by 
lenticels. 
In some instances a formation of callus on the inner surface 
of the pitcher was observed, as described by Treub. This was 
no doubt the result of injury. 
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