390 Slopes .— The Internal Anatomy of ‘Nilssonia orientals'. 
the anatomy of the leaf. There are also several other fragments of the 
same foliage in the matrix. From all these sections the following anatomical 
description is compiled. 
Description of Leaf. 
External appearance. As is seen in the small portion of the leaf shown 
in Fig. i, PI. XXVI, the blade is about 4 cm. across, with a midrib from which 
laterally running veins pass out straight to the margin. These veins are 
about o*5 mm. apart. The character of the venation is better shown in the 
drawing, Fig. 4, PI. XXVI, where the veins are seen to run undivided from 
midrib to margin, as is characteristic for the species in most cases, though 
they may branch a little. 
Internal anatomy. The leaf shows no marked differentiation of an 
upper and lower surface. As there is no palisade tissue, the bundle alone 
exhibits a distinct indication as to which side is uppermost. The sections 
are cut across the lamina, at right angles to the laterally running veins, and 
therefore parallel to the midrib. 
The epidermis . In the well-preserved portions of the leaf the cells of 
the upper and lower epidermes are alike in character, though in the less 
favourably petrified regions those of the lower epidermis are much the more 
obliterated of the two. The individual cells are squarish, about 0-02 mm. in 
diameter, and are not markedly different in size from the mesophyll beside 
them. See e . 1 and e. 2 , Text-figure, and e, Figs. 2 and 3, PI. XXVI. 
The cuticle does not seem to have been noticeably thickened, and there 
is no sign of hairs or protuberances. 
Stomata are not recognizable on the upper surface, which appears to 
have been clothed by an unbroken epidermis. In several sections they are 
to be seen in the lower epidermis, lying in the portion of the leaf between 
the bundles (Text-fig., st). They are not quite perfectly petrified, but the 
guard-cells seem to have been placed at the oblique angle usual in Gymno- 
sperms. 
The mesophyll. The ground tissue of the mesophyll shows no special 
differentiation; the cells are roughly roundish or oblong in shape (see Text- 
fig.), and are arranged so as to leave but little space between them. There 
seems to be none of the differentiated transfusion tissue common in modern 
Cycad leaves. 
Sclerenchyma appears to be developed only in small groups of three 
or four cells above and below the vascular bundles; see sc . 1 and sc. 2 , Text- 
figure. The cells are not very much thickened. 
Resin-canals. I cannot speak dogmatically about the presence or 
absence of these structures. They are certainly not present in the way they 
are in living Cycads, namely, in direct relation to the vascular bundles, 
either between each pair as in Encephalartos or above each as in Dioon. 
