42 0:< Tllli FERTILI2ATI0.y
Httain access to tlie cavity varies greatly in different instances, bafc, allowing for this, there
can be no doubt that larger numbers effect entrance to gall receptacles than is ever the
case with female ones. The following are the data regarding this point as recorded of
a certain number of cases in which the point was specially investigated :—
1. Four young gall-rcceptacles were opened shortly after a largo emergence of
insects l.ad taken place from mature ones on the same tree. In all of them
the corpses of insects were present packed away among the ostiolar bracts:
in two no insects had gained access to the cavity; in one a single insecr
had gained access, but the cavity was still dry; in one twenty in'sects had
entered, the cavity contained some fluid, the ovaries were evidently enlai-ged,
and on microscopic examination unsegmented, pedicellate ova w.ere found
•wiihin the nucelli.
2. A gall-receptacle opened and found to contain the corpses of twenty-four insects
but no fluid.
S. A female receptacle opened fifteen days after insects had been seen to enter
the ostiole. Ten corpses of insects present in the cavity, the ovaries
enlarged, but no fluid yet present.
Five female receptacles opened. All showed evident general ovarian enlargement.
One contained a single insect; one four ; two five ; and one nine.
Four female receptacles with general enlargement of the ovaries opened. All of
them contained several insects.
A female receptacle with general enlargement of the ovaries contained four insects.
A female receptacle full of fluid and containing about 7,000 enlarged ovaries
including well-developed embryos, showed two insect corpses.
8. A female receptacle with about 13,700 enlarged ovaries, including embryos, contained
only one inseet-corpse within the cavity.
9. A female receptacle with universal ovarian enlargement contained a single insect.
10. Six female receptacles with general ovarian enlargement opened. Two contained
one insect; three two ; and one twent3--two.
11. One nearly mature female receptacle with general enlargement of the ovaries
contained three insects with one or two shrunken pollen-grains adherent to
them.
12. A female receptacle with general ovarian enlargement contained one insect.
A female receptacle full of fluid and with general ovarian enlargement contained
four insects.
14. A mature female receptacle full of normal achenes contained one insect embedded
in the gelatinous coating resulting from the softening of the outer coats
of the ovaries.
The above data show clearly that in the case of the female reci'ptacles the results
following access of insects are not proportionate to the nuoibers actually attaining entraace,
and that the entrance of a single insect is sufficient to determine general ovarian enlargement
and tire development of thousands of embryos. The latter fact has been brought out
very clearly in certain special cases. In the first of these à receptacle into which a single
insect had gained access was used as the source whence materials for sections and dissections
of tlie ovaries at an early stage of enlargement were obtained, and in all cases embryos
OP FICUS EOSBUEGHII. ^^
in the earlier stages of evolution were readily recognisable; in the second over eleven
thousand achenes from a mature receptacle containing only one recognisablB insect were
sown and yielded an enormous crop of seedlings.
Those insects which succeed in forcing their way into the rcceptacular cavities immediately
set about attempting to deposit their ova within the flowers. They move actively
about over the surface from one flower to another, and in the case of gall-receptacles rapidly
p t nd o£ their ova, and then die. The site of deposition is invariably within the nucellus
between the epidermis and the loose parenchyma, and at a level with, or a little beneath the
site of attachment of the fanicle, and therefore at some distance beneath the level of
attachment of the base of the style (Plate IV, figs. 14, 16). The deposition must apparently,
fake place, not tid the style, but by means of penetration of the upper surface of the ovary
The external ovipositor is certainly too short to reach even the base of the stvle in many cases'
but, without definite information regarding the length to which the internal portion can be
protruded beyond it, this cannot be regarded as evidence of any groat weight in regard to
the question. The really important evidence lies in the structural feature! of the Sower,
as these show that a very much more direct route to the site of deposition is present from tlie
summit ot the ovary than from the stigma, and one, too, in which the amount of solid
tissue to be penetrated is very much less than in the case of tho stylar route. This is shown
very clearly by the following measurements: —
1. Distance from superior surface of ovary to site of deposition-
Thickness of ovarian wall 0 04 mm
Beptl trom intiPDal surface of ovarian wall to inicropjle, wMcl lies immediaiely
Dtplh from mioropyle to level wher. lie secundinc become, closely'adherent to "
the nuoellua . .
Dcplk thence to site of deposition.' ¿. „ j " '
Told depth from suriaoe ot summit of ovaiy to .ito of deposition' ! ' ' ' ' O'lO
Hepth of really solid tissue to be penetrated ! 0 08
2. Distance from inferior extremity of stylar canal to site of deposition-
Depth of solid portion of style from lower end of stj-lar canal to loner side of
ioner stratum of ovarian wall 016 mm
Depth thence to site of deposit ' ' g,|,g ^ ^
Total dspth of solid tissue to be penetrated ' o-34
It is evident from the above figures that the stylar route reckoned from tho lower
erfremity ot the stylar canal is one-third longer than the other one, end inohdes three
times as large an amount of solid tissue as it does (Plate IV, fig. 19). It is, moreover
much more indirect, as will be clearly evident on reference to the drawing, for the upper
surface of tho ovary lies vertically over tho micropyle and the site of deposition within the
nuoellns, whilst the lower end of the stylai- canal is situated far to one side of the latter It
does not thus appear to be the different form of the stigma and style in normal female and
gall-flowers, which permits of the deposition of ova in the latter and prevents it in the
former. The real determinant is, no doubt, the very great difference in the character and
thickness of the ovarian walls in the two oases. Over the summit of the ovary in gall
Sowers the wall is only about a third as thiok as it is in the correspondino- site in