164 Groom.— On the Function 
reach the hypodermal-layer, beneath which they run for a 
considerable distance, and they finally end either below or 
between its cells. Some tubes descend to the lower epidermis, 
and either end there or turn back into the mesophyll. In one 
case I observed a tube ending on the surface of the leaf 
between the cells of the lower epidermis (Fig. 8). 
In Ficus elastica the tubes can be easily seen passing through 
the aqueous tissue, and ascending to the upper epidermis (see 
also Marcatili’s figure). Their course through the aqueous 
layer is usually oblique. 
In Urostigma sp. (Fig. 9) the distribution of the laticiferous 
tubes in the leaf is very similar to that of Pharmacosycea. 
Tubes pass through the aqueous layer and reach the epidermis. 
Thus in the Artocarpeae there is no considerable subepider- 
mal system as in Euphorbia Peplus. But laticiferous tubes 
may pass right away from the assimilating cells through the 
aqueous tissue. 
Conduction of carbohydrates. In Pharmacosycea sp. carbo- 
hydrates travel along the brown tannin-containing nerve- 
parenchyma-cells. In a few cases the cells of the incomplete 
sheath investing a tube contained more starch than the ad- 
joining cells. But this was only seen when, for some reason, 
the distribution of the starch of the darkened leaves was more 
irregular than usual. 
Papayaceae. 
In the leaf of Carica Papaya there is a considerable vascular 
network close beneath the palisade-layer. So the connection 
between the palisade-cells and the nerve-parenchyma is very 
intimate and direct. The laticiferous tubes form a complex 
anastomosing system. Most of the free tubes merely traverse 
the meshes of the vascular network to connect tube with tube. 
Branches ascend into the palisade-layer ; and Pirotta and 
Marcatili trace some of these branches to the epidermis. 
There is no important subepidermal system of tubes. The 
tubes frequently form an incomplete sheath round the trache- 
ides of the fine vascular bundles. 
