598 Thoday . — Behaviour during Drought of the Leaves of two 
may show, interruption of the palisade layer by fibres, often only in the 
lateral veins, and extending for a variable distance from the tip. The fibres 
appear to be, at least the majority of them, of the ordinary tapering form. 
In leaves higher up, but still juvenile, lateral wandering of fibres from the 
strands associated with the vascular bundles is already found. 
Stomata occur only on the concave upper side. They are not raised, 
but, on the contrary, are sunk below the surface of the epidermis, and flush 
with the inner walls (Fig. 12). 
The majority of the epidermal cells have thick mucilaginous inner 
walls (Fig. 11) which normally occupy a volume about equal to that of the 
Fig. 12. Portion of section of juvenile 
leaf of P. filiformis , showing sunk stomata 
in upper concave epidermis. 
1 , 1 1 1 1 I i 1 11 
hundredths mm. 
Fig. 11. Middle part of 'section of juvenile 
leaf of P. filiformis . Epidermis with mucilaginous 
inner walls ; a few fibres wandering longitudinally 
from the bundle. 
lumen. These cells are very similar in appearance to the epidermal cells of 
Erica spp. According to Supprian, 1 mucilage is found in the epidermis of 
Passerina ericoides , Linn., but not in other species of the genus. It is found, 
however, in some species of most of the genera of Thymelaeaceae, including 
Anlhrosolen and CJiymococca, both closely allied to Passerina . Preliminary 
observations of my own point to a wider distribution of this character in 
Passerina than Supprian recorded, but definite statements are necessarily 
deferred until the species are satisfactorily identified. 
In leaf form, absence of groove and woolly hairs, sunk stomata, and 
mucilaginous inner walls of the epidermal cells the juvenile leaves of 
P . filiformis approximate to those of many other members of the Thyme- 
1 Beitrage zur Kenntnis der Thymelaeaceae. Engler’s Bot. Jahrb., xviii, 1894, p. 310. 
