2 4 O.N THE FEKTILIZATION
two nuclei—one rounded, tlie other oval or rod-like (Plate IV, fig. 7). The pollea does not
t e n d to escape f rom the anthers after dehiscence if the stamens are undisturbed by insects.
The growth oc-om-ring betweeu the period of access of insects and that of maturation is
v e r y great, but up to a comparativaly late period is almost limited to the axes of the flowers.
E l o n g a t i o n of the axis takes place both beneath tho origin of the outer perianth, so that
t h e flower ceases to be sessile, and above it, causing the cL)sed inoer perianth to force the
leaves of the outer one apart and appear prominently beyond them, and forcing the summit
of the terminal portion of the axis with the stamens more and moro against the cupola of
t h e inner perianth. The flower at the same time emerges from within the sheathing bract
and projects beyond it. The filaments for long remain almost unaltered in length while
maturative changes are occurring within the anthers. This is, no doubt, related to the retent
i o n of the stamens within the closed inner perianth, and tho consequent protection of the
a n t h e r s f rom maceration in the receptacular fluid. There is comparatively little increase in
size of the anthers for some time, but the evolution of the pollen goes on, tetrads being soon
replaced b y distinct small grains of normal form. These are at first uninucleate, and measure
about 9'9x6-6^. in diameter. Distinct grains of such character are present within the anthers
a t a t ime wlien the lobes of the outer periant h have only begun to separate and the filaments
show no appreciable elongation. As maturation approaches, and just before the absorption
of the receptacular fluid, the anthers become visibly swollen and the filaments begin to grow
r a p i d l y . As the stamens are still enclosed within the closed cavity of the inner perianth, the
e l o n g a t i n g filaments are not free to grow directly onwards or outwards, but become extremely
folded upon themselves, the basal portion running downwaa-ds along tlie sides of the axis, and
t h e distal halves being folded upwards more or less parallel t o them (Plate IV, fig. 1, a).
T h e inner perianth becomes more and more stretched by the increasing bulk of the
stamens and the upward growth of the terminal portion of the axis from which they arise,
a n d the tension ultimately becomes so great that rupture occurs. As a rule, this occurs at
t h e summit, so that the inner perianth comes to form a cup or funnel around the upper part
of the flower; but in some instances it takes place at the base, and the perianth is then carried
upwards as a cap on the apex of the axis and the stamens until the latter expand and lacerate
it. Kupture of the inner perianth does not usually occur until the absorption of the recept
a c u l ar fluid has taken place, but in exceptional cases it may partially occur before the
fluid has entirely disappeared. Once rupture has taken place, the complete evolution of the
flower occurs with great rapidity. The stamens become widely divergent and protrude
f a r beyond the ruptured perianth (Plate II, fig. 1, b). The extreme protrusion is due partly
t o the tip of the axis rising on the removal of the restraining pressure of the perianth, and
p a r t l y to continued growth in the stamens, but to a much greater extent to mere unfolding
of the filaments. The divergence of the stamens varies in degree in different instances, and is
specially marked in flowers in wliich abortive female organs are present. Dehiscence next
sets in in the faces of the lobes of the oval anthers, but, as previously mentioned, spontaneous
discharge of pollen does not seem to occur.
C.— Characters of male flowers in mature gall-reeepiacles to which in$ects have
not gained access.
I n many cases little or no fai'ther growt h seems to take place after the t ime at which the
receptacle was ready for the access of insects, and the flowers merely undergo a gradual
process of desiccation. In some, however, as has been already mentioned in describing
OP FICUS ROXBUftGHir.
t h e receptacles, a certain amount of evolution occurs, the flowers increasing considerably
i n length and, with their bracts, coming to form an elevated and reflected band around
t h e area of sterHe ostiolar bracts. The flowers only rarely project beyond their proper
bracts, and the outer perianth remains closed, due to the persistent overlapping of its lobes.
T h e following were the measurements of such a flower :
Total height 4 6 mm
Height of stamens ! 2-5 mm!
Breadth from face of onther-lobes to most prominent part of eonneotivo I'O mm.
T h e flowers, thus, in such cases of partial maturation, independent of the access of
insects, acquire dimensions four or five times as great as they have at the proper period
for the occurrence of access. The anthers become much more conspicuous, and acquire
a yellowish-white tint, but tho filaments remain almost unaltered in length (Plate IV, ficr 4)
T r a n s v e r s e sections through the anther-lobes show that tho evolution of pollen" has
advanced to the stage of the formation of tetrads (Plate IV, figs. 5, 6). These form
dense masses surrounded by a double stratum of large tapetal cells, which in its turn
IS for the greater part embedded in tissue the cells of which hare undergone fibrous
resolution. This fibrillation has advanced to the greatest extent between the loculi and
along the central portions of the faces of the lobes. In the latter site even the epidermal
cells have disappeared, and the loculi are only covered by the persistent cuticle and the
subjacent fibrous stratum (Rat e IV, fig. 5). The evolution of the anthers, however, never
advances beyond this stage if insects do not gai n access to the receptacle, and distinct pollengrams
are never formed,
II.—GALL-FLOWERS.
A.—Characters of gall-flowers at the period for access of insects to the receptacles.
The following are the measurements of various specimens, some of the flowers being
sessile and others shortly pedicellate :
1. Averages of sis flowers— '
Height from base of pedicel to summit of ovary 0-456 ram.
Greatest breadtli of ovary 0-436
Length of style aloog its inner side 0-478 mm.
Diameter of stigma o-28o mm!
2. Height from bose of pedicel to stigma, -wliioh at this time is the
highest point mm.
Height from base of pedicel to ovary 427 mm
Greatest breadth of ovary o-399 mm'
Length of style along its inner side o-256 mm.
8. Average length of styles in ten flowers—
Along inner side 0 376 mm
ranging from 0-285 mm to 0 427 mm.
4. Average length of styles in flve flowers—
Along inner edge 0 384 mm,
ANN. EOY. BOT. GARD, CALCUTTA, TOL, I. APPE>-DIX.