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AUG 16 1922 




no. 1-10 

m is 1 922 



Field Museum of Natural History 

Chicago. 1922 

Leaflet Number 1 


"The wild figs upon the fig trees contain a creature 
called psen : this is at first a little worm, and afterwards 
having ruptured the case the psen flies out. and leaves it 
behind. It then pierces the unripe figs, and causes them 
not to fall off. wherefore gardeners place wild fruit near 
rhe cultivated kinds, and plant the wild and cultivated 
plants near each other." — Arisrotle. History of Animals. 
B. V.. Ch. XXVI 3. 

Botanically the figs are a subdivision of the mul- 
berry family. They are peculiar in not having their 
flowers exposed, like most flowering plants, but con- 
cealed within a hollow, urn-shaped receptacle which 
has precisely the appearance of a young fruit. The 
apparent absence of flowers is often a matter for com- 
ment. An old Chinese writer on Materia Medica and 
Natural History in discussing the fig calls it the "fruit 
without flower." In reality the flowers are numerous 
but insignificant in size and in appearance. All other 
members of the family to which the figs belong have, 
like the mulberry, the flowers and the individual fruits 
on the outside. 

Some 600 species of wild figs have been described 
to date. A few of them are cultivated or well-known 
plants, such as the rubber plant which in its normal 
habitat is a rubber yielding tree, the Banyan tree which 
with its numerous proproots may spread over an acre 
or more of ground, and the sycamore fig that furnished 
the everlasting wood for the coffins of the Pharaohs. 
The vast majority of figs, however, grow in semi-tropi- 
cal and tropical forests and jungles as shrubs, trees, or 

2 Field Museum of Natural History 

even as vines. Two species grow native in the sub- 
tropical, southern part of Florida. One of them is a 
so-called "strangling fig." These begin their lives as 
parasites on other trees, growing at first much like 
the mistletoe, but eventually sending their own roots 
to the ground. 

The cultivated fig (Ficus carica) is a native of 
Semitic Asia, perhaps particularly of southern Arabia, 
but occurs also in Syria and in Palestine. Smyrna 
was as famous for its figs in ancient times as it is now. 
From western Asia the Phoenicians and later the Arabs 
carried the fig throughout the entire Mediterranean 
region. The old Greeks scoffed at the barbarians who 
did not have figs and wine. Romulus and Remus, ac- 
cording to tradition, were suckled by a she-wolf under 
a fig tree. In ancient lore the fig occupied a place such 
as does our more familiar apple tree of the Garden of 
Eden. Before the appearance of man, figs grew in 
Europe and in North America. Leaves and fruits like 
those of the cultivated fig have been found fossil in 
France. With the Glacial Period the fig of course dis- 
appeared from the modern temperate zone those 
which now grow in Europe were all introduced horti- 
culturally. Figs have long been grown in China, hav- 
ing been brought by way of Persia from Asia Minor. 
In modern times the cultivated fig has been introduced 
into many lands. It is grown in South and Southwest 
Africa, in South America, and in Australia. It has 
been grown in Sussex in England. It is successfully 
cultivated in the United States, especially in California 
and in the Gulf Region, particularly in Texas. In 
African Sudan where the fig has failed to grow on its 
< iwn roots, it has been grown budded on the more trop- 
ical sycamore fig. 

The cultivated fig is ordinarily a rapidly growing 
small tree with palmately lobed leaves and with a soft 


Figs 3 

wood. It lives sometimes to a great age and then 
reaches large dimensions. It may be uncommonly pro- 
ductive and is said to bear at times a fruit in every 
leaf -axil, though part of such a huge crop is apt to drop 
before maturity. 

As in the case of most cultivated fruits there are 
many varieties. Besides the common fig, called mis- 
sion figs in California, and the well-known Smyrnas, 
a California writer lists Adriatic, Eriocyne, Cordelia, 
and San Pedro figs. The popular distinction into two 
kinds is on the basis of color, purple or "black" figs and 
yellow or "white" figs. The former are usually less 
sweet and are consumed while fresh. The figs which 
come dried and packed in boxes or "drums," such as 
the imported Smyrna figs, are of the white variety. 
They are preserved like raisins or dates by their own 
high sugar content. 

The fig fruit is a hollow, fleshy receptacle, with a 
small opening or "eye" in the top furnishing the only 
point of entry to the interior cavity. Ordinarily this 
opening is almost entirely closed and barred on the 
inside by a zone of small, interlocking scales. The 
inner wall of the receptacle bears the very numerous, 
small, simple flowers which in the edible fig are all of 
the female or pistillate kind, more or less perfect. As 
these grow old and elongate, they completely fill the 
cavity. Each one of them normally matures a single 
small dry seed which in some cultivated figs is always 
sterile, in others fertile when the flowers have been 
pollinated. The fruit of some varieties of the culti- 
vated fig "ripens," i. e., the receptacle becomes soft, 
fleshy and edible, without pollination. The fruit of 
others will not ripen unless pollinated. 

Pollination is a normal occurrence in the wild fig 
only. This, in contrast to the edible fig {Ficus) bears 
partly inedible fruit and is known as the goats-fig-tree, 


4 Field Museum of Natural History 

" Capri ficus" or Caprifig. It is also known as the 
"male fig" because its figs or flower receptacles con- 
tain male flowers in addition to the others. Female 
trees of the wild fig also exist but are very scarce. 
The edible fig is undoubtedly derived from such. The 
male flowers of the Caprifig are situated in the upper 
part of the fig cavity, immediately below the scales, 
which here as in the edible fig, bar the opening to 

The insect which ordinarily inhabits the interior 
of the fig cavity is the minute Fig Wasp (Blastophaga 
grossorum, family Chalcidae). Through the course 
of ages of association (fossil figs have been found in 
remains of the Cretaceous period) the life history of 
the fig and of the minute wasp have become inextric- 
ably entangled. Complete interdependence has been es- 
tablished between them, so that each is necessary for 
the existence of the other. Without the wasp the wild 
fig would soon become extinct, for there would be no 
maturing of seed, and, vice versa, in the absence of 
the wild figs there would be no fig wasps hatching. 
The female fig wasp enters the young caprifig in which 
at a certain period the orifice is relaxed, lays its eggs 
in the short-styled flowers near the base of the cavity 
and dies within the fig. These flowers are known as 
gall flowers. The habit of response to the visitations 
of the fig wasp has proceeded to the stage of anticipa- 
tion, for gall flowers are not normal flowers that be- 
come gall flowers through the egg-laying of the insect, 
but are already present as such, though barren and 
useless till the puncture of the wasp supplies them an 
inhabitant in the shape of a wasp grub. 

The eggs hatch into male and female wasps. The 
small, yellow, wingless males mature first, bite holes 
in their galls and crawl out into the cavity of the fig. 
They soon cut holes in the gall flowers containing the 


Figs 5 

still immature females, impregnate them and shortly 
die within the fig, as did the mother wasp. 

Their sisters, the female wasps, are darker, of a 
brown color and winged. In due course they hatch 
and immediately set about leaving the cavity of the 
fig within which there is no room for them to spread 
their wings. To reach the orifice of the fig they must 
pass the male flowers and become dusted with the 
pollen that matures at the very time of their hatching 
and departure. 

Once in the open air their wings soon dry and each 
young female wasp is off in search of an immature 
fig in which to deposit eggs. A suitable one found, the 
wasp proceeds to cut a notch in one of the outer scales 
for better access, then makes its way inside. In the 
process the wasp generally loses its wings. These are 
apt to stick in the opening, so that an inhabitated fig 
may be recognized by their presence. The pollen car- 
ried by the insect is brushed off on the stigmas of the 
long-styled flowers within. Eggs can be properly 
placed only in figs of the Caprificus kind, where gall 
flowers are present. 

Both the wild and the cultivated fig usually bear 
three crops a year. As insects emerge from one crop 
of maturing Caprifigs they ordinarily find green fruit 
of the next crop ready to receive them. Each crop is 
thus pollinated with pollen of the preceding crop. An 
interval of about two months elapses between the en- 
trance of the egg-laying fig wasp into the young fig 
and the emergence of her progeny from the ripe one. 
The same interval of time separates the receptive stage 
of the female fig flowers and the ripening of the pollen 
in the male flowers, completely excluding the possibility 
of self-pollination. The last of the fig wasps of the 
year deposit their eggs in young fruit which stays on 
the trees until spring. 


6 Field Museum of Natural History 

To prevent the dropping of fruit of the edible fig 
before maturity, it is an ancient practice among fig 
growers to hang branches of the wild fig tree, or 
strings of ripe Caprifigs, in the trees of the fig orchard. 
The fig wasps will then enter the young edible figs and 
bring about pollination with the Caprifig pollen. The 
true Smyrna fig absolutely requires pollination to ripen 
its fruit. Fig trees of this variety grown in Califor- 
nia continued to drop their immature fruit for over 
twenty years till the wild fig with its fig wasp was 
introduced and the so-called "caprification" was made 
possible. In Mediterranean countries Caprifigs for the 
purpose of caprification are an article of commerce 
at times bringing a higher price than edible figs. It has 
often been stated on apparently good botanical author- 
ity that the practice is of doubtful utility. According 
to the California zoologist, Eisen, who has done much 
to clear up this question, the confusion is due to a fail- 
ure to discriminate between the varieties which require 
and those which do not require pollination in order to 
mature their fruit. The latter kind are grown alto- 
gether in some localities, as in southern France. 

The ancients who observed the fig wasp and well 
knew that it had something to do with the ripening of 
the fruit, sought to account for it in accordance with 
the ideas of their time., e. g., "the wasps suck up the 
superfluous humors," "they enlarge the eye and per- 
mit the fertilizing air to enter." 

The German botanist, Solms-Laubach was the first 
to investigate thoroughly the flowers of the fig and 
extended his inquiries to some of the numerous species 
of wild Ficus. Many of these have been studied since 
and relations have been found to exist between plant 
host and insect tenant similar to those observed in the 
cultivated fig. The insects associated with the wild 
figs are all closely related to the fig wasp of the Capri- 


Figs 7 

fig but distinct and different in the various species of 
the genus Ficus. It would seem probable that most, if 
not all, of the six hundred or more species of wild figs 
throughout the world are as dependent for their con- 
tinued existence on their respective fig wasp guests as 

is the Caprifig. 

B. E. Dahlgren. 

Exhibits in the Field Museum pertaining to the Mulberry 
Family and the Fig are to be found in the Department of Botany, 
Halls 28 and 29, particularly, a reproduction of a fruiting branch 
of the Cultivated Fig, an enlarged section of a young flower 
receptacle, an enlarged section of a Caprifig with the male and 
female Fig Wasps, wood and rubber of Ficus, etc. 

In the Department of Geology, Hall 18, are to be seen fossil 
Figs, of the Cretaceous period, from Wyoming and Kansas. 



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