Range - Setis

“ . . . discal expansion forming a narrow rim beyond the calyx-teeth.” (Specific
description of E. tetrodonta.)
“ . . . discal lining generally much extended beyond the ovary.” (Generic
definition of Eucalyptus—“Eucalyptographia.”)
The following are synonyms:—
Discal-lining.
Floral disc (flower).
Capsular disc (fruit).
Let us begin with some preliminary observations.
Disc or Discal-lining. In E. Preissiana, E. megacarpa, E. globulus, and E. alpina,
which we take as examples, the thick band or expansion at the top of the fruit is an
enlargement of the floral disc. Its development in the fruit or capsule can be traced
from the floral stage. In all species examined it varies somewhat, but its presence, as
far as I have observed, is indicated by the usually dark zone or lining at the base of
and on the sides of the calyx-tube. In the species mentioned, the pulvinate gland-like
processes are present on the floral disc, and as the ovary develops, so also does the
disc. As the ovary develops, it grows upwards and outwards, and apparently more
so in the centre, until it is carried, with the disc, beyond the level of the calycine
rim. The rim then increases in thickness, and at the same time gradually extends
over the valves of the capsule, but in all cases leaves the tips of the valves free. In E.
Preissiana the disc is entirely free from the valves, and forms a thick crenate layer
above them on the inner margin, while the outer edge is fused to the calycine
portion of the capsule. The disc therefore derives its nutriment from the calycine
portion, and not from any portion of the valves or ovary.
The term “discal-lining” applied by Mueller to some species is a very appropriate
one, for in the species mentioned the calyx-tube cup is deep, and has a dark carnose
lining which extends towards the ovary in a wave or crenate line, and is
differentiated from the ovary by the colour, that of the latter organ being always
much paler. The discal lining is naturally more noticeable in species with large
flowers and fruits. The term could be conveniently used in descriptions when the
disc is obscure, because it is, like the disc, an important character, as it is very
largely responsible for the morphosis of the fruit.