454 MESSRS. J. PARKIN AND H. H. W. PEARSON ON THE 
of the leaf have a much swollen appearance. In surface view 
they appear lenticular in shape (PI. 12. fig. 7): in section they 
present the form of pegs, being thickest next the outer wall and 
diminishing gradually towards the basal one (Pl. 12. fig. 6). 
Treatment with Schultze’s solution or iodine and sulphuric acid 
shows that the cuticularized part of the outer wall is continued 
down these side-walls for some distance in the form of wedges 
(PI. 12. fig. 6, ep.); but no cuticularized core is revealed in the 
ordinary thin lateral walls. 
An examination of young leaves makes it evident that these 
peculiar walls are interpolated after the general cellular forma- 
tion of the epidermis. In fact, they may be regarded as 
belonging to the same category as those walls which are inserted 
so as to render an epidermis two-layered ; only in the first case 
the additional walls are radial, while in the second case they are 
tangential. The original cell is usually well defined, as it is 
bounded by the ordinary thin lateral walls; it may remain 
single or be divided into two or more compartments by the 
formation of these special walls (Pl. 12. fig. 7). The latter 
result is best seen in the epidermis overlying the vascular 
bundles (veins). They, no doubt, serve to strengthen the leaf, 
and may perhaps to some extent help to lessen transpiration. 
This peculiarity does not seem to have been noticed previously 
in the genus. 
The leaf of this plant is also interesting as possessing an 
isobilateral structure. ‘Till quite recently all species of the 
Hypericacee * examined possessed dorsiventral leaves with 
stomata only on the lower surface. Kearney t, in a paper 
published lately, mentions two other species of the genus, viz. 
Hypericum virgatum, Lam., and H. pilosum, Walt., as having 
isobilateral leaves. In both these species, growing in an exposed 
situation, the leaves are erect and, as in H. mysorense, the 
stomata are found on the ventral as well as on the dorsal 
surface, the epidermal cells of both surfaces present similar 
characters, and a second palisade-layer is found contiguous with 
the lower epidermis. 
(8) Mucilaginous Cells in the Epidermis.—The presence of 
mucilaginous cells in the epidermis is a common character of 
* Solereder, Syst. Anat. Dicot. (1899) pp. 134-135. 
t Kearney, Contr. from U.S. Nat. Herb. vol. v. (1901) pp. 495, 496. 
