262 MR. В. S. ADAMSON ON THE COMPARATIVE ANATOMY 
few chloroplasts and have much vacuolated contents. They occupy nearly 
half the thickness of the leaf (fig. 12). They seem to form a kind of water- 
tissue. Stomata are confined to the lower side. А few hairs occur along 
the furrow above the vertically transcurrent central bundle. 
Grrour Е. 
In this group are plants with very much reduced leaves. The reduction 
has resulted in various forms : e. g., V. lycopodioides and V. tetrasticha have 
an ericoid appearance, while V. //ectori has the leaves completely clasping 
the stem with no free portion ; again, in V. cupressoides the leaves are very 
small and thick, and do not cover the whole internode as they do in the other 
species of this group. With the exception of V. tetrasticha, the xylem 
elements of the leaf-bundles have very much thickened walls, so that the 
lumina of the cells are almost obliterated in some cases *. 
V. loganioides, Armst. 1. 
The leaves are reduced, but spreading; they are stiff, with clasping bases. 
Stomata are more numerous on the upper side. The leaves are rather thick, 
with several layers of palisade-cells ; the spongy tissue consists of closel 
V ] ? I ey y 
aacked rounded cells. The bundles, as in all the species in this group, are 
I ? I , 
embedded. 
V. epacridea, Hook. f. 
The leaves are small and appressed when young. Stomata occur in 
moderate numbers on both sides. The mesophyll is composed of palisade- 
like cells. The xylem in cultivated material is normal, but in material from 
Cheeseman's herbarium it shows the great thickening referred to above. 
V. lycopodioides, Hook. f. f. 
The leaves are stiff and awl-shaped. The epidermis of the upper and 
outer parts has much thickened cuticularized walls. Stomata are confined 
to the free point. The mesophyll near the tip is very homogeneous (fig. 13), 
but in the lower part there is greater differentiation ; a layer of water-tissue 
occurs along the upper (7. e. inner) side, and a layer of palisade-cells occurs 
along the lower side. Cork is developed at the leaf-base. 
V. tetrasticha, Hook. f. 
Externally the leaves are very like those of V. lycopodioides, but are not so 
stiff and are broader. Stiff bristle-like hairs occur along the margins below. 
The epidermis of the free parts consists of large cells with their outer walls 
very much thickened and cuticularized. The mesophyll is like that of 
V. lycopodioides, but the bundles, both in cultivated and herbarium material, 
are very small, with normal xylem. 
* Cf. IIuchedé (1907). + Bot. Mag. t. 7404. і Dot. Mag. t. 7338. 
