AND HISTOLOGY OF PIPER BETLE. 367 
eccentric funnel. The mouth of this funnel measures about 8 р in diameter, 
while its bore is З ш. Downwards it broadens into an angular body (PI. 18. 
fig. 21). The thickened parts of the wall are cutinised (fig. 17). 
The cell constituting the body of the hair lies horizontally and is oval in 
outline (Pl. 18. fig. 20). From a surface-view it measures about 45 u by 12 р. 
It is inserted nearer one end. The two ends are not quite symmetrical ; 
the proximal end is more rounded, and the distal end or free tip is bluntly 
pointed and sometimes shows lamellated thickening (Pl. 18. fig. 15). In 
height the cell measures as much as it does in breadth, The cell is so 
orientated that the extending slope of the eccentric funnel points towards 
its longer tapering arm. With reference to the entire leaf they have 
not any definite direction. Although the basal cell lies in a shallow 
depression, the back of the hair slightly projects above the general surface 
(РІ. 18. fig. 17). The hairs just described are of the nature of hydathodes ; 
they readily absorbed colouring-matter when the leaf was immersed in an 
extremely dilute solution of methylene-blue (1 in 500.000). This indicates * 
an ability to absorb water from outside when necessary and available. Тһе 
funnel-like thickening of the basal cell seems to be intended to facilitate the 
passage of water either way. The cell constituting the body of the hair 
strongly reminds one of similar hairs (hydathodes ? +) found on the leaves 
of Camptothera acuminata, Decne., among the Cornacere. 
Smail-celled patches.—These are constituted by the epidermal cells forming 
an aggregation of cells that are characterised by their small size, being 
about a fourth of the usual size of normal epidermal cells. A patch generally 
measures 60 ш across, The cells vary in their frequency from 200 to 400 
per square centimetre, They also differ greatly in their structure, Та the 
simplest case there is nothing remarkable, except the small size; in other 
cases one or more of the hydathodes may be included within its limits. 
Another difference may be in one or more of the ceils appearing more 
refractive than the rest, and finely dotted. Lastly, such an ageregation 
may lie distinctly above the general surface ; it focuses, when examined 
from surface-view, differently from the rest of the epidermis and a part of 
its edge does not fit in with the surrounding cells, but it clearly overlaps 
them. 
The hypodermal cells lying beneath the patches are also modified, in as 
much as their walls are thickened and strongly silicified. On the other hand, 
the epidermal cells are thin-walled. It is highly probable that these patches 
form an apparatus accessory to the hydathodes, but it is not clear how they 
operate ; the silicification of the hypodermal cells is intended to prevent 
collapse of the water-tissue. This is analogous to the occurrence of idio- 
* Warming's ‘(Ecology of Plants, Engl. ed. p. 945. 
+ Solereder's * Systematic Anatomy of Dicotyledons, Engl. Trans. p. 456. 
