BOTANY OF THE CEYLON PATANAS. 453 
VII. Spectan Points tn THE ANATOMY OF THE LEAF 
BEARING ON XEROPHYTISM. 
Under this heading are enumerated certain leaf-structures in 
some of these plants, such as a double-layered epidermis, 
mucilage-cells, &c., which are generally regarded as protections 
against excessive transpiration; also instances of chloroplasts 
occurring in the epidermal cells—usually looked upon as a 
decidedly mesophytic character. 
(1) *A Double-layered Upper Epidermis or Hypoderm occurs in 
Glochidion zeylanicum, Heptapleurum stellatum, Psidium Guyava, 
thododendron arboreum, Vernonia Wightiana, and Exacum 
zeylanicum. 
Glochidion zeylanicum. The upper epidermis is not uniformly 
two-layered, but only double in places. This fact does not seem 
to have been recorded for the genus. . 
Heptapleurum stellatum. The upper epidermis is 2-3 cells 
deep, as a rule two; the second layer is deeper than the first. 
The genus is mentioned by Soleredert as possessing a 
hypoderm. 
Psidium Guyava (Pl. 11. fig. 7). The upper epidermis con- 
sists of 3-4 narrow layers of cells. Bokorny { has noted a 
hypoderm in the species P. araca and P. incanescens. 
Rhododendron arboreum. The upper epidermis is composed 
of two layers of about equal depth. This instance is recorded 
by Solereder. 
Vernonia Wightiana. The epidermis is divided in places 
only. 
Exacum zeylanicum. Below the uppermost layer of cells 
(epidermis) is one composed of large, rather rounded cells with 
very few chloroplasts; it appears to have been differentiated 
from the mesophyll, and probably functions as an aqueous layer. 
(2) Peculiar Lateral Walls in the Epidermis of Hypericum 
mysorense.—Some of the lateral walls of both epidermal layers 
* In none of these examples, except Exacum zeylanicum, has it been 
definitely proved whether the second layer of cells may have been derived from 
the originally single epidermal layer or from the mesophyll. Immature leaves 
in various stages were not to hand to settle this point. Most likely all but 
Exacum are epidermal in origin. 
t Solereder, Syst. Anat. der Dicotyledonen, 1899, p. 482. 
t Bokorny, Flora, 1882, pp. 35-45 & p. 387; also Soler 3 Pe 398. 
