32 THE FERTILIZATION
apes also a great accumulation of cells is present, forming a solid [jlug containing five or sis
strata which fills the micropylar orifice and projects somewhat beyond it (Plate V, fig. 1).
The cells in both the basal and micropylar thickenings difier in form from those ia the rest
of the epidermal stratum, as they are square or polygonal in place of flattened.
Within the epidermal stratum is a coating of delicate, loose cellular tissue surrounding
the large embryo-sac. This also presents basal and apical thickeniugs T^here the tissue
becomes much denser and more coherent than it is eleswhere (Plato V, figs. 1, 7). The
basal thickening consists of many superimposed strata of cells, which are frequently
associated so as to form more or less distinctly defiued lobes (Plate V, fig. 7). The apical
thickening is very peculiar (Plate V, fig. 1). It forms a dense, broadly conical mass capping
the apex of the embryo-sac. The constituent cells are closely adapted to one another, are
quadrangular or polygonal in outline, and contain relatively large, deeply-staining nuclei.
Centrally the cap is of great thickness, containing six or seven strata of cells (Plate V, fig. 1),
I t thins oS all round peripherally, and gradually subsides into the surrounding loose cellular
tissue covering the lateral surfaces of the embryo-sac. Under the influence of the reagents
employed in mounting permanent specimens of ovules, and specially of entii-e ovules, the
inner nucellar coat frequently shrinks away from the epidermal one save at the base, so as to
leave a clear space between them (Plate V, fig. 8). The "walls of the cells do not show the
brownish tinge with picrocarmine which those of the epidermal stratum do, and the large
nuclei, save in the apical thickening, stain comparatively feebly.
Within the general mass of nucellar parenchyma, as this stratum may be conveniently
termed, and immediately ai-ound the embryo-sac, a certain number of small flattened cells,
appearing fusiform in profile, are present (Plate V, fig. 1). These are most abundant, as a
rule, towards the apex of the nucellus. Immediately beneath the apical cap, and attached to
one of its constituent ceils, is a large and peculiar cell of this type (Plate V, figs. 1, 2, 3, 4, 5, 6).
I n sectional view it appears as a curved spindle with the centre of the convex surface
attached to the under surface of the apical cap, and the prominence of the concave one in
contact -with, or in close relation to, the outer surface of the apes of the embryo-sac. This
prominence is sometimes very marked, and where the embryo-sac has not shrunk too far
away in the course of preparation of the specimen, it often appears to depress its apes, while
the two pointed extremities of the spindle project free on either side as lateral horns (Plate
V, %. 6). The entire body of the spindle is characterised by staining very deeply,
especially with logwood.
The centre of the nucellus is occupied by a huge embryo-sac, with a delicate membranous
wall, a network of finely molecular protoplasm, and a large nucleolate nucleus (Plate V,
fig. 3). There do not, as a rule, appear to be any oosphere, synergidas, or antipodal
cells. Only in one case have I been able to detect anything which might possibly be taken
to represent an oosphere and synergids, and in that the appearances were doubtful, and such
as could only correspond with elements of very abortive character.
B.^ Character8 of female Jliiwers shortly aftef access of imecU to the receptacles.
The following show the measurements of a pedicellate flower a few days
of insects to the receptacle:—
Total heiglit from base of pedicel to summit of ovary 3-02 mn
Height from base to origin of the perianth 1'34 mn
Total height of ovary 0-79 mu
r t h e access
r OF FICUS EOSBUEGHII.
Breadth of ovary at loTel of upper edge of stylar iomi ion . . . f'fin mm.
Height from upper edge of stjlar iosertioa to summit of ovary . 0-51 mm.
Total longtli of style and stigma 1 56 raiu.
Breadth of stigma
These figures very clearly indicate the ocourrenoe of rapid growth in the ovaries and in
the case of pedicellate flowers, in the pedicels subsequent to the access of insects The
perianth retains its previous dimensions, and the ovary consequently comes to project more
and more from it. Even at the early stage represented by the flowers of which measurements
have been given, the summit of the ovary rises high above the tips of the perianth
I h e o n gm oi the style, just as in the case of the gall-flowers, appears to descend due to
ezcessive growth in the upper part of the ovary, and in some cases the colour of the nooer
parts of the styles and the stigmata gradually changes from rose-madder to brick-red
Eeyond this neither styles nor stigmata show any change, and, with the exception of the
basal portion of the style, which ultimately becomes softened, remain persistent up to the
period of maturation of the seeds and long after the outer coats of the ovary have unlr„„,
mucoid degeneration The wall, of the ovary gradually thicken, the increase being maTn]y
due to changes takmg place in the two inner strata; the cells of the internal e p iZmt
increaang in depth and in the thickness of their walls, and processes of cell multiplicrtrn
occurring in the stratum of small cells lying external to them. The general increa» T Z
bulk of .he Sowers even within a few days subsequent to access of insects to the receptacTe
IS so considerable as to be very evident even to casual inspection by the unaided e e
I h e important phenomena are those manifesting themselves in the ovuL. The e when
removed from the ovaries a few days after access of insects to the receptacles and e x i t
in water and uncovered so as to avoid flattening, give diameters of aLut O-SlxO-sTmm
T e secundrne and nucellar epidermis show no important changes save those dependenrrn
extension, due to increased bulk of the deeper parts of the nucellus, but conspilus
changes soon set in n the nucellar paronchyma and embryo-sac. In the orme C T s
firstly, general growth around the sides of the embrycsac, and secondly, special growt a ts
base and apex. The cells of the loose tissue of the parenchyma begin to i n c r e a s e l " th y
s.am much more deeply than they did previously, and there is an obvious accumula on 3
protoplasm w i t t n them (Plate V, fig. 9). Beneath the base of the embryo-sac t ™ a 1 »
lation of cells becomes thicker and denser than it was before, and in some »ses, at all eveTs
a peculiar local outgrowth takes place on its upper surface, giving rise to a p omineS
circular mound of very small-celled tissue surrounding a centra! depression, and a larnf l y
strongly cuticularised on the surface (Plate V, fig. 16). As it is developed, it push , up J
invagmates the lower end of the embrjo-sac. r , P i» up ana
The walls of the cells of the apical cap generally become considerably thickened, but do
not otherwise show any appreciable change. Ths. special ceU attached to its under smface
and which appears as a deeply-stained spindle in section, on the other hand, under„e;
very remarkable development. It swells up centrally, and at the same time th penl "
portions shoot out into large processes and beoome gradually separated by partition, f ! . ? ! ?
central di atahon (Plato V, %s. II, 12). In sections it wou'd appear Z Z Z t V ^ :
d e J m g with changes cccurring in a simple spindle, but, judginffrom the —. - a r c
present in some cases in entire or pai-tially-disseoted ovules, it ap^ar s to be p r o b X thatTn
reahty the cell originally consists of a central more or le.ss c o n L mass with „ « a M t ^ d
Ak-.i. Eov. Hot, G.iiin. C..Loorij, Vol.. I. Amxms.