40 OiN THE FERTILIZATION
to a mere heap of umbcr-colonred Mrii and detached stamens, filaments, anthers, and
pollen.grains. Having done so, they encounter the much more formidable obstacle pre.
sented by tbe pkg of ostiolar bracts. Here tliey set to work mnch more methodically
no longer gnawing right and left at random, but confining their operations to the centre
of the plug, through which they eventually succeed in tunnelhng an evenly cylindrical
channel of exit loosely filled with soft brown dUri, and struggling insects (Plate IV, fi» 2i)
I t .s, of course, difEcnlt to determine the precise lengih of the intervals elapsing between
the disappearance of the receptacular fluid and the emergence of the male insects into the
cavity, and from the latter to their exit from the perforated ostiolum. They probably vary
considerably m different instances, especially the latter, which must necessarily be directly
related to the number of male insects present. The following are the only data regarding
this point which are attainable :— o s
1. A mature receptacle was taken in the morning. At noon male insects were
beginning to emerge from the ostiolum in large numbers, and at 5 p.m.
females were beginning to appear.
2. A large mature receptacle was taken in the morning. A few male insects emerged
from the ostiolum during the course of the day and on the following
morning, and were then followed by multitudes of females during the course
of the forenoon. Here the emergence of the females was apparmtly delayed,
due to the defective number of males present to clear the way for them.
3. A large matm-e receptacle was taken in the morning. At 4 p.m. one mab had
actually emerged and others could be seen struggling deep down in the
ostiolar tunnel. By 7 a.m. of the following morning numerous males had
emerged, and females were emerging and flying off in a continuous stream,
and by 9 a.m. emergence had ceased.
4. A mature receptacle was laid open by transverse division, and was found to contain
a large number of free female insects and a comparatively small number of
males, who were already hard at work demolishing the male flowers and
beginning to attack the ostiolar plug. The ostiolar half of the receptacle
was put aside under a bell glass with the open surface of the receptacular
cavity upwards. Twenty-four honrs later perforation of the ostiolar plug
had been completed, and a considerable number of male insects had
emerged from the orifice and were lying about beneath the under surface
of the specimen. As there was no evidence to show that any had escaped
over the cut edges of the receptacle, the purely reflex character of the
process of tunnelling was strikingly demonstrated.
Having effected their exit, such of the male insects as escape immediate seizure by
tlie predatory ants which are usually on the wait for them fall down from the receptacle and
very soon die. Under normal circumstances the winged female insects begin to emerge
from the receptacles shortly after the completion of the ostiolar tunnel, appearing for°a
time in company with the males, and, after these have all emerged, continuing to issue forth
alone for a considerable time. But all receptacles are not alike in their insect contents,
l a normal cases the male insects, although by no means so abundant as the females, are
yet present in sufficient numbers to secure rapid and thorough perforation of the ostiolar
plug ; in others they are still present, but in unduly small numbers, so that there is delay
OP FIOUS EOXBUEGHIL ^^
in perforation ; and in a third class they are entirely ab,<ent. Where no males are present,
the females still emerge in enormous numbers from the ovaries into the receptacular cavity'
but, as they are incapable of perforating the ostiolar ping, they remain imorisoned and di¡
without ever gaining exit to the outer world. The same thing also happens U e n the
number of males is extremely reduced and insuflicient to secure completion of the tunnel
of exit. If such receplnclcs be laid open ere the death of the inmates, the interior of tlie
cavities presents a most remarkable appearance, the lower part being blackened by a dense
mass of struggKng females, who at once begin to fly off in clouds into the surrounding air
When the females emerge by the normal route, they sometimes fly off dite"ctly' on
reaching the external orifice of the tunnel, but they usually remain for a few minutes close
to it drying their wings, which are often clogged with moisture, and cleaning of particles
of débris which have adhered to them and to the rest of the surface of the body durino- the'
outward journey. The amount of adherent « n i is always insignificant, and appears
mainly to consist of the amber-coloured dust of the gnawed stamens and ostiolar scales No
doubt pollen grains are also present, as one or two may occasionally be found still adheriinr
to the eoipses of insects in the cavities of freshly-entered receptacles, but the number
always be comparatively small, and is never sufficient to give rise to any appearane»
recognisable by the unaided eye or under a simple lens. l'i-uiiances
Very large numbers of the female insects fall immediate victims to the watchful
which swarm around the months of the tunnels, and those who escape soon fly ofi wl
many large receptacles are emitting simultaneously, a perfect cloud of them fill a "
sm:rounding air. The majority of them conth.ue for some time hoverin. about in th
neighbourhood of the site of exit, and then, where receptacles suitable for the pm-nose
present, they settle down and attempt to gain access to the cavities. They are how
capable of ffying for a considerable distance, for the only female tree of F Itàb.roh"''
the Botanic Garden in Calcutta is situated at a distance of about a quarter of a m-I f
the nearest male ones, and yet crops of figs to which female insect, have attained J T .
are constantly present on it. Tie insects have a certain power of discriminating
fades which are at the suitable stage for them from those which have either not°.t„;„ J
to or have exceeded it. The distinctive feature would seem to lie in some condition ofTh
ostiofc bracts, as insects may often be seen alighting on the sm^faces of apparently suit
able receptacles, rnnning eagerly over them up to the ostiolar area, entering its conLvitv
and, after scufn.amg it, emerging again and ffying off in search of another ¡ ^ ZSj'
thn, ,s the case, they are at the same time incapable of distinguishing gall f,„°„ ,
receptacles, and struggle as energetically to enter the latter as the former m.
they have found a suitable one, they at once set about the arduous task of forciu"
way m through the solid ostiolar plug of closely apprsssed, overlapping stiX l T
w icb in gall-receptacles has a thickness of about O-S", and in f ema l e 'L. ' L n t L f
wha thicker, measuring in many cases as much as 0.43-. The relative sises of T n » c h
ostiolar plug are shown in Plate III, fig 1. »»d
Where insects are present in abundance, the ostiolar depression, of suitable recen, ,
frequently become crowded by masses of struggling visitors attempting to force tllTr '
down between the bracts, and casting their wings as they do so. They graduallv di l n
from view, and a certain proportion of them ultimately succeeds in gaming a ceÍ t f r
receptacular cavity. Large numbers of them, howeveí never do so, but p i sh" ¡se .
between the sticky bracts, where their bodies remain readily recognisable for montT ^
up to the period of maturation of the receptacles-as dark bro wn 0 b a c kTr a t a " " ?
wiched between the appressed surface, of the bracts. The number of insecÏwboTventraBy
AUK. BOY. BOT. Gjru. Ostcum, TOL. I. Amuuii,