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A FOSSIL FLOWER
Published by
FIELD MUSEUM OF NATURAL HISTORY
CHICAGO
1924
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Field Museum of Natural History
DEPARTMENT OF BOTANY
Chicago, 1924
Leaflet Number 5
A FOSSIL FLOWER
One of the last official signatures of President
Harding was affixed to an act establishing the Cycad
National Monument, the story of which forms an
interesting chapter in the history of recent botanical
science.
The tract of land in the southern Black Hills of
Dakota thus designated and now set apart "for all
time" is neither especially distinguished for grandeur
of landscape, magnificence of present vegetation, nor
for other openly striking features. Nevertheless it
is a place justly famous among botanists the world
over.
The locality had attracted attention nearly a cen-
tury ago. In the course of the adventures related by
Edgar Allan Poe in The Thousand-and-second Tale
of Scheherazade, Sinbad and his companion encoun-
tered an island "where the forests were of solid stone,
and so hard that they shivered to pieces the finest-
tempered axes. . . ." In a footnote to this tale there is
mentioned by way of corroboration "the discovery
of a completely petrified forest near the head waters
of the Cheyenne, or Chienne River, which has its
source in the Black Hills of the Rocky chain."
That an unparalleled record of extinct life of the
Reptilian Age lies imbedded in the rocks of this for-
mation was scarcely suspected until about thirty years
ago. It was not until then that the locality received
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2 Field Museum of Natural History
scientific attention 1 and some of its fossil tree
trunks were described. They had been looked upon
mainly as remains of fairly well-known cone-bearing
plants, though among them had been noted stems,
suggestive of both tree-ferns and so-called sago
palms. These were determined to be fossil cycads
of a type already known, especially in Europe, but
more perfectly preserved than any hitherto seen. The
fame of the locality, however, rests chiefly on the
subsequent and surprising discovery that many of
these fossil trunks bore actual flowers. These were
brought to light by Professor Wieland of Yale 2 .
Indicating that real floral structures had originated
much earlier than had heretofore been supposed,
these ancient and primitive flowers differ in many
respects from those of the later true flowering plants
and have proved to be botanically of extraordinary
interest.
The plants which bore these flowers flourished
millions of years ago, 3 when egg-laying monsters
were still extant. The common name "Cycadeoid"
1. Professor Thos. H. Macbride of Iowa published the
first description of a Black Hills cycad in 1893. Professor
O. C. Marsh of Yale soon afterwards made a very extensive
collection of the trunks. Professor Lester F. Ward made
several reconnaissances of the region and described numerous
species of these fossils.
2. Less extensive material of similar kind in less per-
fect stages of petrification had also been studied by European
botanists, but without finality of results, when Professor G. R.
Wieland in 1898 began his searching investigation of the
Black Hills material, both in the field and laboratory. He
was soon able to report surprising discoveries, and to make
some of the most critical and important additions to paleo-
botany, or the knowledge of ancient plants, in perhaps a gen-
eration.
3. The age of the formation in which they were found
has been variously estimated. On the basis of the disintegra-
tion rate of radio-active minerals it exceeds a hundred
million years.
The earliest known cycadeoid remains date from the
Triassic, the latest from the Cretaceous. Their distribution in
time thus covers the entire Mesozoic. The foliage type is
even older.
[42]
A Fossil Flower
Fig. 2.
A LIVING CYCAD.
(Dioon edule).
The living cycads constitute a small and dwindling group, confined^ almost
exclusively to the tropics. The "armour" formed by old leaf-bases remaining on
the trunk, is a characteristic feature of the cycads, plainly to be seen in this fine
photograph of a Mexican plant.
Photograph by Professor C. J. Chamberlain.
[43]
4 Field Museum of Natural History
meaning cycad-like, is from the generic name Cycade-
oidea used about a century ago by the celebrated Dean
Buckland 4 for specimens of their kind from the Isle
of Portland on the south coast of England. The
Cycadeoids are related to the living cycads which in-
clude some so-called Sago Palms, and resemble them
in stem structure and foliage, yet the presence of
flowers places them in a separate group. Being en-
tirely extinct, they are commonly and not incorrectly
spoken of as "fossil cycads", as by using this term
in a wide sense the cumbersome technical name is
avoided. During the Reptilian or Mesozoic Age, the
medieval era in the history of life on earth, the fossil
cycads probably constituted at least a third of the
vegetation. This age is therefore also known as the
Age of Cycads. On the basis of its chief vegetation
the succeeding Age of Mammals, which includes the
present day, is characterized as the Age of the Flower-
ing Plants. However, it was shown by Professor
Wieland's investigations that the dominant types of
the vegetation even in the mid-geologic era, had
reached an actual flowering stage.
Some plants of the Cycadeoid group were small-
leaved and branched, and in general appearance must
have been comparable to the simpler forms of modern
trees. They were no doubt the very numerous for-
est members of their kind. The great mass of the
petrified forms which have been discovered were
thick-stemmed, globular to low columnar plants, most-
ly unbranched, though some are forked after the
manner of cacti. They grew probably on the edge
of deserts.
4. English clergyman and geologist, author of the Bridge-
water Treatise on Geology, Dean of Westminster. Buckland
had advised with Robert Brown, the botanist, who suggested a
family name, the Cycadeoidese. The term Bennettiteae is pre-
ferred by some botanists.
[44]
A Fossil Flower 5
Trunks of the thick-stemmed kind have been
found in a few localities in Europe, in Afghanistan
and in India. One such petrified stem, now in an
Italian museum, was found in an old Etruscan necrop-
olis or burial place near Bologna, where it had been
•r— ." r ^L ^*
Fig. 3.
A FOSSIL CYCAD TRUNK.
(Cycadeoidea dacotensis).
Numerous large fructifications enclosed by their bracts are conspicuous
among the pits which mark the ends of the leaf-bases. This magnificent silic-
ified trunk was the first specimen described from the Black Hills.
Courtesy of Professor T. H. Macbride.
placed on a tomb by the Etruscans who obtained it
from the near-by Apennine hills over four thousand
years ago. About a thousand of these trunks have
been discovered in the United States. The great mass
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6 Field Museum of Natural History
of them comes from the Black Hills of Dakota, the
most numerous and important specimens being ob-
tained from within the actual limits of the Cycad
National Monument. Others have been found in Wy-
oming, also in Maryland between the cities of Wash-
ington and Baltimore, and isolated stems have been
collected in Texas, Colorado and California. They
were early recognized as fossils, although not always
suspected to be plants. Their appearance is unusual
and has attracted attention wherever they were found.
The miners in the Potomac region kept them as curi-
osities in their homes, regarding them as fossil bee-
hives and wasp-nests. The workmen in the quarries of
Portland, England, where they are encountered, long
ago dubbed them "crows-nests." As in the cycads, the
leaf bases in these plants remained after the foliage
wilted down and now make up the outer layer, or
"armour", of the trunks, at the surface of which the
spirally disposed ends usually appear as depressions or
pits. On this account the trunks were described by
some early writers as petrified "masses of coral-cups"
or as "clusters of barnacles."
Professor Wieland found his fossil flowers secure-
ly encased in this outer layer of the trunks. They
were present mostly in the form of unexpanded buds
but in many instances fruits had begun to mature.
No actually open flowers have ever been found. Nat-
urally any that were present when the chain of events
leading to fossilization began, wilted and must have
been quickly destroyed, as may be easily surmised
after a glance at the delicate expanded structure. It
was the fortunate preservation of the well-protected
buds in a petrified state that made possible the inves-
tigation of their nature. It is likely that these ex-
tinct plants, like the century plant or the Talipot palm,
flowered only once after a prolonged vegetative
period, and then died down. The flowering must have
[46]
A Fossil Flower
Figr. 4.
A FOSSIL CYCAD IN FLOWER.
This figure represents the conception of the famous paleobotanist, Nalthorst.
The original painting is in the National Museum, Stockholm.
Courtesy of Professor G. R. Wieland.
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Field Museum of Natural History
been profuse, for some of the trunks preserved in the
critical stage show upwards of five hundred buds.
The position of the flowers on the old part of the
trunk is unusual, but is not entirely unique, for a
somewhat similar flowering habit is to be seen among
some of the tropical forest trees.
Fig. 5.
A FOSSIL CYCAD FLOWER.
(Cycadeoidea ingens).
Photograph of the model in the Field Museum of Natural History.
By the use of a tubular drill, Professor Wieland
removed the buds and fruits from the petrified trunks.
The cores thus secured were sliced and polished, so
that the structures enclosed became plainly exposed
[48]
A Fossil Flower
9
to view. The preservation is often so perfect that
microscopic details, such as pollen grains, may be as
clearly observed as in living plants, and the study of
an abundance of sectioned material has resulted in a
clear comprehension of the structure.
The most striking feature of one of these flowers
Fig. 6.
A FOSSIL CYCAD FLOWER.
(Cycadeoidea ingens).
Photograph of the model in the Field Museum of Natural History. Same as
figr. 5, seen from above.
is its branched stamens, which number a dozen or
more, resembling the fertile fronds of certain ferns.
The stamens are laterally united at the base and
fused to a corolla-like "disk." The disk with the
[49]
10 Field Museum of Natural History
stamens was thrown off as soon as the function of the
latter was fulfilled. Similar but simpler disks had
previously puzzled geologists who found them as
detached specimens in various places. The center of
the flower is occupied by a seed-producing cone, as is
the case in the magnolias, especially in the tulip
tree. In its minute structure the fossil cone is,
however, quite different from that of these flowering
trees, for the seeds are still naked instead of enclosed
as in the present true flowering plants. Below the
disks are numerous bracts, or "sepals", as they would
be called in a modern flower. These constituted an
outer protecting envelope which remained to surround
the fruit as it matured. All the usual parts of a flow-
er are seen to be present and disposed in the usual
sequence. This fossil flower is thus unmistakably a
flower according to all definitions — "the flower of
Linnaeus, of Goethe, and of Payer", as their discov-
erer states.
It is quite natural to ask, what may be the con-
nection between these ancient flowers and those of
the modern flowering plants.
The origin of the flowering plants proper is ob-
scure. Their first appearance as leaf -impressions in the
rocks dates from the latter half of the Age of Cycads.
From the numbers and the considerable variety of
their earliest traces, it is certain that they were then
already far advanced. A long evolutionary history,
which remains unknown, unquestionably lies behind
their sudden rise to visibility. It was this late and
apparently abrupt appearance of the flowering plants
that was referred to by Darwin as an "abominable
mystery."
In the absence of fossil clues, the origin of the
now dominant flowering plants is an unsolved prob-
lem in spite of the intensive study of living plants that
has been carried on for generations. Botanists are
[50]
A Fossil Flower
11
not agreed as to which of the many kinds of flower-
ing plants may be assumed to be most primitive and
to represent the nearest approach to an ancestral type.
Indeed, botanical classification of the flowering plants
is expressive of the uncertainty which prevails.
Such being roughly the state of our knowledge
— or ignorance — of the origin and primitive state of
the true flowering plants, the question inevitably
arises whether the ancient flowers of the fossil cycads
Fijr. 7.
A schematic flower of a hypothetical stock ancestral to
cycads and flowering: plants.
From Arber and Parkin.
may not represent the ancestral type. The particular
one described and figured here is considered much too
specialized to be the ancestor of anything. It must
rather be considered, with the plants to which it be-
longed, to have been an end-product, or a final devel-
opment in a vanishing line. However, some flowers
of simpler fossil cycads of a less peculiar habit of
growth have also been discovered. The degree of rela-
tionship of the fossil cycads to the stock from which
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Field Museum of Natural History
the flowering plants sprang has not been defined, but
the consensus of opinion seems to be that the two
lines are at best only distantly connected. The near-
est relationship that appears to be possible is a con-
nection by common descent from a still older group.
Nevertheless it is difficult to escape the growing
conviction that these fossil flowers shed light on the
early floral structure of the true flowering plants. It
is tempting to assume, at least by the way of hypothe-
Fig. 8.
A purely hypothetical primitive flower of the true
flowering plants.
From Arber and Parkin.
sis, that the ancestors of these bore flowers organized
on a similar plan. 5 The well-known English author-
ity, Scott, thus says of the cycadeoid flowers, that they
"for the first time brought the origin of the flowering
plants within the range of scientific discussion."
The alterations which would be required to trans-
form the cycadeoid flower into that of the later flow-
ering plant can easily be specified. Restorations of
5. "The cycadeoid flowers show the possibilities and
trends of variation and even the lines along which variation
could primarily occur." Wieland.
[52]
A Fossil Flower
13
hypothetical ancestral flowers have been attempted
by Wieland and others on this basis and visualized by
the English botanists Arber and Parkin as reproduced
in Figures 7 and 8. If their conception is accepted
as correct in principle, the so-called "strobilus theory"
of the flower becomes the only tenable one. Accord-
ing to this the various parts of the primitive flower
were disposed in the form of a cone, terminal on the
flowering axis. Its seed-bearing members were placed
Fig. 9.
A TULIP-TREE FLOWER.
The carpels are seen to form a strobilus or cone. In the magnolia the stamens
are more numerous and arranged in a more definitely spiral manner.
From Sargent.
at the tip, followed in order by stamens and below
these by the sterile members which are generally
known as petals and sepals. The parts are assumed
to be indefinite in number, and spirally arranged. The
most primitive flowers, according to this theory, are
those of the magnolia order, with the tulip tree flower
approaching perhaps more closely than any other to
the ideal type.* This well-known theory has long been
entertained by many botanists who now find support
Wieland, 1901.
[53]
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Field Museum of Natural History
for their views in these fossil flowers. Others, more
skeptical, refuse to attach any special significance to
the older cycad floral type taken as a hypothetical
"missing link."
Fig. 10.
Stages in the reduction of stamens from the frond-like condition
in fossil cycad flowers (1. Cycadeoidea, 2. WiUiamsonia), through a
hypothetical intermediate stage (3), to the condition in a flowering
plant such as the morning-glory (4).
From Wieland.
The presence of the bell-shaped disk uniting the
stamens has led to some speculation, particularly
since it has also been found in another cycadeoid with
[54]
A Fossil Flower 15
unbranched stamens. Professor Wieland 6 points out,
that with the stamens reduced to simplest form, this
disk or "campanula" would make a perfect corolla
of the morning-glory type. The possibility is sug-
gested that this feature may have been present also
among some members of the primitive flowering stock
and that the origin of the corolla of many flowers
of the tubular type may be far more ancient than is
is ordinarily supposed. Such are a few of the botani-
cal questions which are raised.
Entirely apart from their theoretical importance
and possible bearing on the evolutionary history of the
flowering plants, these early flowers are in them-
selves objects of great interest. Considering the per-
ishable nature of flowers and the delicate character
of many of their parts, the fact of their perfect pres-
ervation through millions of years seems remarkable.
To bring to light and to restore with confidence ex-
tinct flowers which bloomed at the time when the
earliest birds were learning to fly is no small achieve-
ment. The published results of Professor Wieland's
investigations fill two large illustrated volumes issued
by the Carnegie Institution of Washington, and a
third, of equal interest, published by the Geological
Institute of Mexico.
Realizing the desirability of conserving the site
that yielded these fossil trunks, Professor Wieland
had the foresight to secure its immediate protection by
filing a homestead claim to the tract of 320 acres. It
is due to his initiative that this tract, which he later
released for the purpose, is now preserved as a Nat-
ional Monument of unique botanical interest.
A reconstruction or model of this fossil flower
as restored by Professor Wieland has been produced
with his cooperation in the Stanley Field Laboratories
6. Wieland, G. R., Botanical Gazette, Dec. 1909.
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16 Field Museum of Natural History
of the Field Museum of Natural History. It will be
placed near the modern cycads in the hall devoted in
this Museum to a synopsis of the plant-life of the
world.
B. E. Dahlgren.
Fossil Cycad trunks and leaves are found in the ex-
hibits of the Department of Geology in the west hall (Hall
38) on the second floor.
In the Department of Botany the Cycads are to be seen
in the Hall of Plant Life, in the east hall (Hall 29), also on
the second floor.
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