100 MR. J. H. BURRAGE ON THE 
tively short, a large number of functionless dises are only 
separated from the support by the thickness of the stem. Those 
disces on the other side of a stem which is in contact with a 
surface are often nearly as large as those which actually fasten 
the branch to it. In this case the development and subsequent 
changes proceed very similarly in both, with the exception that, 
unless in a very damp position, the hairs of the dise not in con- 
tact are shorter, and the formation of the cork cambium takes 
place much earlier than in those dises applied to the support. 
It is difficult, however, to decide how much of this development of 
functionless discs is due to the action of moisture. In all cases 
the first stages of development are initiated much later than in 
the normal disc, and the further growth is much more irregular. 
In some the formation of hairs is confined to a small central 
area, the epidermis remaining intact over the greater portion, 
which projects but little from the stem. Small dises are occa- 
sionally formed on branches some way removed from any support, 
in which the hairs are fully developed—evidently stimulated to 
growth by moisture. Similarly, discs in various stages of corky 
degeneration may be found, but in all cases smaller than those 
near to the support. In some semi-developed dises the walls of 
the columnar cells become suberized, the epidermis still remain- 
ing above, consisting of empty cells with thickened walls. In 
this case the epidermis has probably been severely strained by 
the pressure from the growing tissues beneath it, which necessi- 
tates the formation of a corky layer, as a check to evaporation. 
On branches excluded by position from proximity to a support 
or a damp medium, there are no traces of discs in any stage of 
development. 
The position of the discs in the axils of the leaves is appa- 
rently ill adapted for purposes of climbing. The twisting of the 
petiole brings the blade of the leaf into a more favourable posi- 
tion for the performance of its functions, but even then, in the 
case of a flat surface, some four out of six of the dises are of no 
use in supporting the plant, since the leaves are arranged in a 
2 spiral. The general appearance of the plant suggests a 
scrambling nature, and one well adapted for creeping among 
loose stones or climbing over larger shrubs. 
The vertical position of many of the leaves, their funnel-shaped 
lamina and grooved petiole with expanded sheath, suggest the 
possibility of the dises absorbing water, which must necessarily 
