2 8 ON THE PEETILIZATIOH"
certain amount of active protoplasmic accumulation, ard even of cell mnltiplication, appears
to take place in the deeper nucellar tissue. The cells of the latter appear to be rich in
protoplasm, and stain deeply with carmine, and at some points specially deeply-stained patches
are present which appear to correspond with localised centres of specially active growth (Plate
IV, fig. U). Towards the apex of the nucellns there is generally a special accumulation of
cells beloHgiiig to the deeper stratum, but these do not differ from their neighbours elsewhere,
aud never form a dense coherent mass like the apical cap of the deeper nucellar tissue in
normal female flowers (Plate IV, fig. 15). The nucellar epidermis presents features very
similar to those characterising it previous to the access of insects. It forms a thin stratum
over the greater part of the sm-face, becoming somewhat thicker at the base of the nucellus,
and forming a plug at the micropyle. The latter is now relatively much smaller than it was,
and is no longer vertical and at the summit of the ovule, but is directed to the funicular side'
and often situated almost vertically over the funicle (Plate IV, fig. 14). The increase in
vertical diameter of the ovule evidently takes place much more in a descending than an
ascending dh-ection, for the distance between the upper edge of the funicle and the micropyle
and apes of the ovule remains comparatively short, while the raphe has undergone great
elongation. The funicle and the secundine have now gi'eatly reduced relative proportions,
the former appearing as a short narrow cord, and the latter as a mere thin investing stratum.
The increased bulk of the ovule is evidently principally determined by a great accumulation
of fluid within the embryo-sae distending it and stretching the surrounding tissues.
The insect-ovum is not merely situated within the ovary: it is deposited within the ovule
or, more exactly, within the nucellus, lying between the epidermal stratum and the loose
tissue surrounding the embryo-sac, at a point just below the insertion of the funicle (Plate IV,
figs. 14, 16). It is pcdicellate and of a long oval forcu, the pedicel being attached to the
loose cellular tissue of the deeper nucellar coat (Plate IV, fig, 17). It has apparently two
walls—an external one, with which the pedicel is connected, and an internal one around the
large granular mass of protoplasmic contents. It is evident that considerable growth must
occui- subsequent to deposition and antecedent to the commencement of cleavage, as the bodies
of ova at this period give diameters of O'lOS x 0-0342 mm., and contain a dense mass of
protoplasm measuring 0-08Ó5 x 0'0342 mm., whereas the spherical ova expressed from the
bodies of female insects at the time of access have a diameter of only about 0'067 mm. and
contain a netted protoplasm (Plate IV, figs. 17, 18). The pedicel is about O'Oo in length, and
the lower extremity is slightly dilated (Plate IV, fig. 17).
Subsequently, during the period when the development of the insect is occuixing, very
little actual growth of ovular tissues occurs, the inner coat of the nucellus and the embryosac
appear to atrophy and disappear completely, and the nucellar epidermis and secundine
become gradually converted into a delicate sheath investing the body of the embryo. The
inner cells of this sheath, presumably representing the nucellar epidermis, become greatly
estended in surface and altered in form, and the stretching of the tissue tends to separate them
from one nnother, so that large intercellular intervals come to be present among them. At the
same time they bccome very poor in protoplasm, but retain their nuclei for a very considerable
time (Plate IV, fig. 20).
The walls of the ovary increase in thickness, but to a much less degree than in the true
female flowers, the depth in mature ones not being more than double what it is at the period
of access. Figure 25 of Plate IV shows the appearance of the ovarian wall in a gall-flower
approaching matuiity. It shows that very considerable increase in the size of the cells, and
OP FICÜS EOXBÜEGHir. 29
specially extension in their areas, has occurred. The external epidermis is thickly cuticularized,
and the walls of the internal epidermis and the stratum external to it are considerably
thickened. There is no softening of the external sti'ata of cells similar to that occurring in
the ovaries of true female flowers during maturation.
The total increase in bulk of the gaU-fiowers during maturation is enormous, and far
exceeds that occurring in the case of the true female ones. The ovaries ultimately become
about three times as large as they were at the period of insect access, and in many cases
there is excessive growth in the pedicels. The actual length of pedicels in mature flowers
varies greatly. In some cases the flowers remain almost or quite sessile; in others the
pedicels may be as much as eight times longer than they are in any pedicellate flowers at
the period of access. There is little or no increase in size in either the perianth or the
style and stigma subsequent to insect access. In matm-e flowers the perianth forms a mere
cup around the base of the enlarged and projecting ovary, and the styles, in place of being
at one siide of the apex, arise so far down the lateral surfaces that the stigmas are situated at a
lower level than the now rounded summits of the ovaries (Plate II, fig. 3).
C.—Charaeiers of gall-fiowers in mature receptacles to which insects have
not attained access.
A certain amount of growth occui's, so that the flowers externally come to resemble those
in receptacles shortly after the access of insects. The following are the measurements of a
tall pedicellate flower:—
Total height from base of pedicel to stigma 2-707 D
Height to lower part of ovary i-gg n
Height to base of ovule n
Height from level of origin of perianth to top of ovaiy 1-08 n
L e n g t h of style 0-627 n
Diameter of stigma 0-313 n
Diameters of ovule 0-4275 x 0-285 n
The ovule is reduced to the condition of a dry thin-walled sac surrounding the large
empty cavity of the embayo-sac. The increased size of the flowers is mainly due to growth in
the pedicels, as the perianth still curves over the top of the ovary.
I I I . — T E O E FEMALE FLOWERS.
A.—Characters of female flowers at the period of access of insects to the receptacle.
{Plate I I , fgs. 5, 6).
As in the case of the gall-flowers, while the size of the ovaries is fairly constant at this
;e, that of the flowers as a -whole varies considerably, due to the fact that while some aro
sile, others have pedicels of vaiying length (Plate III, fig. 5).