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Rapidly permineralized fossils can provide exceptional insights into the evolution of life over geological time. Here, we present an exquisitely preserved, calcified stem of a royal fern (Osmundaceae) from Early Jurassic lahar deposits of Sweden in which authigenic mineral precipitation from hydrothermal brines occurred so rapidly that it preserved cytoplasm, cytosol granules, nuclei, and even chromosomes in various stages of cell division. Morphometric parameters of interphase nuclei match those of extant Osmundaceae, indicating that the genome size of these reputed “living fossils” has remained unchanged over at least 180 million years—a paramount example of evolutionary stasis.
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23. W. K. Kroeze, D. J. Sheffler, B. L. Roth, J. Cell Sci. 116,
48674869 (2003).
24. J. S. Gutkind, Sci. STKE 2000, re1 (2000).
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Acknowledgments: We thank the anonymous reviewers for their
thoughtful and insightful critiques, which substantively improved
this manuscript. Supported by the Singapore University of Technology
and DesignMassachusetts Institute of Technology International
Design Center (IDG31300103) and by Natural Sciences and
Engineering Research Council (Discovery Grant 125517855).
Supplementary Materials
Materials and Methods
Figs. S1 to S4
Tables S1 and S2
References (2670)
18 June 2013; accepted 31 January 2014
Fossilized Nuclei and Chromosomes
Reveal 180 Million Years of
Genomic Stasis in Royal Ferns
Benjamin Bomfleur,
*Stephen McLoughlin,
*Vivi Vajda
Rapidly permineralized fossils can provide exceptional insights into the evolution of life over geological
time. Here, we present an exquisitely preserved, calcified stem of a royal fern (Osmundaceae)
from Early Jurassic lahar deposits of Sweden in which authigenic mineral precipitation from
hydrothermal brines occurred so rapidly that it preserved cytoplasm, cytosol granules, nuclei, and even
chromosomes in various stages of cell division. Morphometric parameters of interphase nuclei match
those of extant Osmundaceae, indicating that the genome size of these reputed living fossilshas
remained unchanged over at least 180 million yearsa paramount example of evolutionary stasis.
Royal ferns (Osmundaceae) are a basal
group of leptosporangiate ferns that have
undergone little morphological and an-
atomical change since Mesozoic times (16).
Well-preserved fossil plants from 220-million-
year-old rocks already exhibit the distinctive ar-
chitecture of the extant interrupted fern (Osmunda
claytoniana)(2), and many permineralized os-
mundaceous rhizomes from the Mesozoic are
practically indistinguishable from those of mod-
ern genera (35)orspecies(6). Furthermore, with
the exception of one natural polyploid hybrid
(7), all extant Osmundaceae have an invariant
and unusually low chromosome count (7,8), sug-
gesting that the genome structure of these ferns
may have remained unchanged over long periods
of geologic time (8). To date, evidence for evo-
lutionary conservatism in fern genomes has been
exclusively based on studies of extant plants
(9,10). Here, we present direct paleontological
evidence for long-term genomic stasis in this
family in the form of a calcified osmundaceous
rhizome from the Lower Jurassic of Sweden with
pristinely preserved cellular contents, including
nuclei and chromosomes.
The specimen was collected from mafic vol-
caniclastic rocks [informally named the Djupadal
formation(11)] at Korsaröd near Höör, Scania,
Sweden [fig. S1 of (12)]. Palynological analysis in-
dicates an Early Jurassic (P li ensbachian) age for
these deposits (11) (fig. S2), which agrees with
radiometric dates obtained from nearby volcanic
necks (13) from which the basaltic debris or igina ted.
The fern rhizome was permineralized in vivo by
calcite from hydrothermal brines (11,14)thatper-
Department of Palaeobiology, Swedish Museum of Natural
History, PostOffice Box 50007, SE-104 05 Stockholm, Sweden.
Department of Geology, Lund University, Sölvegatan 12,
SE-223 62 Lund, Sweden.
*Corresponding author. E-mail: benjamin.bomfleur@ (B.B.); (S.M.)
Fi g. 1 . Cytological features preserved in the apical region
of the Korsaröd fern fossil. (A) transverse section through
the rhizome; (B) detail of radial longitudinal section showing
typical pith-parenchyma cells with preserved cell membranes
(arrow), cytoplasm and cytosol particles, and interphase nuclei
with prominent nucleoli; (C) interphase nucleus with nucleolus
and intact nuclear membrane; (D) early prophase nucleus with
condensing chromatin and disintegrating nucleolus and
nuclear membrane; (Eand F)lateprophasecellswithcoiled
chromosomes and with nucleolus and nuclear membrane
completely disintegrated; (Gand H)prometaphasecells
showing chromosomes aligning at the equator of the nucleus;
(Iand J) possible anaphase cells showing chromosomes at-
tenuated toward opposite poles. (A), (C to E), (G), and (I)
are from NRM S069656. (B), (F), (H), and (J) are from NRM
S069658. Scale bars: (A) 500 mm; (B) 20 mm; (C to J) 5 mm.
21 MARCH 2014 VOL 343 SCIENCE www.sciencemag.org1376
col ated through the coarse-grained sed iment s shor t-
ly after deposition (table S1). The fossil is 6 cm
long and 4 cm wide and consists of a small (~7 mm
diameter) central stem surrounded by a dense man-
tle of persistent frond bases with interspersed rootl ets
(Fig. 1). Its complex reticulate vascular cylinder
(ectophloic dictyoxylic siphonostele), parenchym-
atous pith and inner cortex, and thick fibrous outer
cortex are characteristic features of Osmundaceae
(1,35,12) (fig. S3). Moreover, the frond bases
mantling the rhizome contain a heterogeneous scle-
renchyma ring that is typical of extant Osmunda
sensu lato (1,3,4,12) (fig. S4). The presence of
a single root per leaf trace favors affinities with
(sub)genus Osmundastrum (1,3,6,12).
The specimen is preserved in exquisite sub-
cellular detail (Fig. 1 and figs. S4 and S5). Pa-
renchyma cells in the pith and cortex show
preserved cell contents, including membrane-
bound cytoplasm, cytosol granules, and possible
amyloplasts (Fig. 1 and fig. S5). Most cells con-
tain interphase nuclei with conspicuous nucleoli
(Fig. 1, figs. S4 and S5, and movies S1 and S2).
Transverse and longitudinal sections through the
apical part of the stem also reveal sporadic dividing
parenchyma cells, mainly in the pith periphery
(Fig. 1). These are typically preserved in prophase
or telophase stages, in which the nucleolus and nu-
clear envelope are more or less unresolved and the
chromatin occurs in the form of diffuse, granular
material or as distinct chromatid strands. A few
cells contain chromosomes that are aligned at the
equator of the nucleus, indicative of early meta-
phase, and two cells were found to contain chromo-
somes that appear to be attenuated toward opposite
poles, representing possible anaphase stages.
Some tissue portions in the stem cortex and the
outer leaf bases show signs of necrosis and pro-
grammed cell death (fig. S6).
Such fine subcellular detail has rarely been
documented in fossils (1517) because the chances
for fossilization of delicate organelles are small
(16) and their features are commonly ambiguous
(17). The consistent distribution and architec-
ture of the cellular contents in the Korsaröd fern
fossil resolved via light microscopy (Fig. 1 and
fig. S4), scanning electron microscopy (fig. S5),
and synchrotron radiation x-ray tomographic
microscopy (SRXTM) (fig. S5 and movies S1
and S2) provide unequivocal evidence for three-
dimensionally preserved organelles.
Positive scaling relationships rooted in DNA
content can be used to extrapolate relative ge-
nome sizes and ploidy levels of plants (1821).
We measured minimum and maximum diame-
ters, perimeters, and maximum cross-sectional
areas of interphase nuclei in pith and cortical
parenchyma cells of the fossil and of its extant
relative Osmundastrum cinnamomeum.Themea-
surements match very closely (Fig. 2), with mean
nuclear perimeters of 32.2 versus 32.6 mmand
mean areas of 82.2 versus 84.9 mm
in the fossil
and in extant Osmundastrum, respectively. The
equivalent nuclear sizes demonstrate that the
Korsaröd fern fossil and extant Osmundaceae
likely share the same chromosome count and DNA
content, and thus suggest that neither ploidization
events nor notable amounts of gene loss have
occurred in the genome of the royal ferns since
the Early Jurassic ~180 million years ago [(8),
see also discussion in (9,10)]. These results, in
concert with morphological and anatomical evi-
dence (16), indicate that the Osmundaceae rep-
resents a notable example of evolutionary stasis
among plants.
References and Notes
1. W. Hewitson, Ann. Mo. Bot. Gard. 49,5793 (1962).
2. C. Phipps et al., Am. J. Bot. 85, 888895 (1998).
3. C. N. Miller, Contrib. Mus. Paleontol. 23, 105169 (1971).
4. G. W. Rothwell, E. L. Taylor, T. N. Taylor, Am. J. Bot. 89,
352361 (2002).
5. N. Tian, Y.-D. Wang, Z.-K. Jiang, Palaeoworld 17,
183200 (2008).
6. R. Serbet, G. W. Rothwell, Int. J. Plant Sci. 160, 425433
7. C. Tsutsumi, S. Matsumoto, Y. Yatabe-Kakugawa,
Y. Hirayama, M. Kato, Syst. Bot. 36, 836844 (2011).
8. E. J. Klekowski, Am. J. Bot. 57, 11221138 (1970).
9. M. S. Barker, P. G. Wolf, Bioscience 60, 177185 (2010).
10. I. J. Leitch, A. R. Leitch, in Plant Genome Diversity,
I. J. Leitch, J. Greilhuber, J. Doležel, J. F. Wendel, Eds.
(Springer-Verlag, Wien, 2013), vol. 2, pp. 307322.
11. C. Augustsson, GFF 123,2328 (2001).
12. See supplementary materials available on Science Online.
13. I. Bergelin, GFF 131, 165175 (2009).
14. A. Ahlberg, U. Sivhed, M. Erlström, Geol. Surv. Denm.
Greenl. Bull. 1, 527541 (2003).
15. S. D. Brack-Hanes, J. C. Vaughn, Science 200,
13831385 (1978).
16. K. J. Niklas, Am. J. Bot. 69, 325334 (1982).
17. J. W. Hagadorn et al., Science 314, 291294 (2006).
18. A. E. DeMaggio, R. H. Wetmore, J. E. Hannaford,
D. E. Stetler, V. Raghavan, Bioscience 21,313316 (1971).
19. J. Masterson, Science 264, 421424 (1994).
20. I. Símová, T. Herben, Proc. Biol. Sci. 279, 867875 (2012).
21. B. H. Lomax et al., New Phytol. 201, 636644 (2014).
Acknowledgments: We thank E. M. Friis and S. Bengtson
(Stockholm) and F. Marone and M. Stampanoni (Villigen) for
assistance with SRXTM analyses at the Swiss Light Source, Paul
Scherrer Institute (Villigen); G. Grimm (Stockholm) for assistance
with statistical analyses; B. Bremer and G. Larsson (Stockholm)
for providing live material of Osmunda;M.A.GandolfoNixon
from the Cornell University Plant Anatomy Collection (CUPAC;; the members of Tjörnarps
N. Tian (Shenyang), Y.-D. Wang (Nanjing), and T. E. Wood
(Flagstaff, Arizona) for discussion; and two anonymous referees for
constructive comments. This research was jointly supported by the
Swedish Research Council (VR), Lund University Carbon Cycle
Centre (LUCCI), and the Royal Swedish Academy of Sciences. The
material is curated at the Swedish Museum of Natural History
(Stockholm, Sweden) under accession nos. S069649 to S069658
and S089687 to S089693.
Supplementary Materials
Materials and Methods
Supplementary Text
Figs. S1 to S6
Table S1
References (2236)
Movies S1 and S2
17 December 2013; accepted 21 February 2014
Fig. 2. Morphometric
parameters of inter-
phase nuclei of extant
O. cinnamomeum com-
pared to those of the
Korsaröd fern fossil. Col-
ored box-and-whiskers plots
in upper graph indicate
interquartile ranges (box)
with mean (square), me-
dian (solid transverse bar),
and extrema (whiskers);
dashed colored lines in
lower graph indicate linear
fits (n=76versusn=37
measured nuclei for extant
O. cinnamomeum versus
the fossil). SCIENCE VOL 343 21 MARCH 2014 1377
Supplementary Materials for
Fossilized Nuclei and Chromosomes Reveal 180 Million Years of
Genomic Stasis in Royal Ferns
Benjamin Bomfleur,* Stephen McLoughlin,* Vivi Vajda
*Corresponding author. E-mail: (B.B.); (S.M.)
Published 21 March 2014, Science 343, 1376 (2014)
DOI: 10.1126/science.1249884
This PDF file includes:
Materials and Methods
Supplementary Text
Figs. S1 and S6
Table S1
Captions for Movies S1 and S2
Other Supplementary Material for this manuscript includes the following:
(available at
Movies S1 and S2
Materials and Methods:
Standard 30 μm thin sections (22, 23) of the fossil and of extant Osmundastrum were
studied with an BX51 compound microscope (Olympus; Vendelsö, Sweden) and
photographed using an DP71 digital camera (Olympus). Nuclear parameters were
measured using cellSens© Dimension version 1.6 (Olympus Soft Imaging Systems;
Münster, Germany), and analysed using Origin© version 8 (OriginLab; Northampton,
MA). Transverse and radial longitudinal surfaces of the permineralized rhizome were
polished and then etched in 5% HCl for 5–10 seconds; after drying, these specimens were
sputter-coated with gold for 90 seconds, and examined and imaged using a S-4300 field
emission scanning electron microscope (Hitachi; Krefeld, Germany) at the Swedish
Museum of Natural History (Naturhistoriska Riksmuseet). In addition, a portion of a
permineralized stipe (petiole) was removed and analysed using synchrotron X-ray
tomographic microscopy at the TOMCAT beam-line of the Swiss Light Source, Paul
Scherrer Institute (Villigen, Switzerland) [see (2426)]. The tomographic data were
processed and reconstructed using Avizo© Fire version 8 (FEI Visualization Sciences
Group; Hillsboro, OR). We applied conventional adjustments of brightness, contrast, and
saturation to the digital images using Adobe© Photoshop© CS5 Extended version 12.0
(Adobe Systems Incorporated; San Jose, CA).
Five samples of the host rock (NRM S069690, NRM S069730, NRM S06738, NRM
S069740, and NRM S069644) were processed for palynological analysis following the
standard methods at Global GeoLab Ltd. (Medicine Hat, Canada). One entire strew slide
per sample was analysed for presence/absence data, and 200 palynomorphs per sample
were counted for relative abundance data where possible.
Measurements of major and trace elements were obtained using a Niton XL3t
Goldd+ X-ray fluorescence (XRF) analyzer (Thermo Scientific; Örebro, Sweden) at the
Department of Geology, Lund University; calibration and drift detection was undertaken
using standard sample NIST 2709a with known reference values. The volcaniclastic host
rock (sample NRM S069645) and a polished surface of the fern fossil (sample NRM
S069649) were both analyzed for elemental constituents over target areas of 8 mm
diameter. Fossil material (NRM S069649–S069658) and measured slides of extant
Osmundastrum cinnamomeum (NRM S089694) are housed in the Department of
Palaeobiology at the Swedish Museum of Natural History, Stockholm, Sweden.
Supplementary Text
Palynological dating:
The samples yielded low- to moderate-diversity assemblages of non-marine
palynomorphs, including spores, pollen, and fresh-water algae. Abundance data were
assessed for samples NRM S069690 and NRM S069730, which are both dominated by
fern spores (52% and 63%, respectively) followed by gymnosperm pollen grains (33%
and 43%, respectively). Taxa occurring in high relative abundances include the spores
Osmundacidites wellmanii Couper 1953 (Osmundaceae: up to 12% in sample NRM
S069690), Cyathidites minor Couper 1953 (Cyatheaceae), Deltoidospora toralis
(Leschik) Lund 1977 (Matoniaceae, Dicksoniaceae, Cyatheaceae, or Dipteridaceae), and
Marattisporites scabratus Couper 1958 (Marattiales). Gymnosperm pollen grains are
mainly represented by Perinopollenites elatoides Couper 1958, Classopollis spp.,
Alisporites spp., Chasmatosporites spp., and Eucommiidites troedssonii Erdtman 1948.
Additional taxa include Striatella seebergensis Mädler, 1964, Retitriletes clavatoides
(Cookson 1953) Döring et al. in Krutzsch 1963, Spheripollenites psilatus Couper 1958,
and a few specimens of Cerebropollenites thiergartii Schulz 1967 and Vitreisporites
pallidus (Reissinger) Nilsson 1958.
The high relative abundance of fern spores, Chasmatosporites spp., and Alisporites
spp. together with the scarcity of Classopollis and Spheripollenites psilatus and absence
of Toarcian key-taxa (e.g., Clavatipollenites hughesii and Callialasporites spp.) indicate
a late Pliensbachian age for the assemblage. The spore-pollen suite correlates with the
Sinemurian–Pliensbachian Cerebropollenites macroverrucosus Zone (27) and with the
Pliensbachian Chasmatosporites Zone (28)established in southern Scandinavia. It also
closely matches palynofloras from the late Pliensbachian Assemblage Zone 3
(ChasmatosporitesCerebropollenites thiergartiiBotryococcus Zone) (29) and the late
Pliensbachian Assemblage A (A2) (30) established in Greenland.
A further important observation is the unusually common occurrence of large, intact
clusters of Marattisporites scabratus Couper 1953, indicating a short transport distance
for the palynomorphs.
List of taxonomically diagnostic characters of the permineralized fern rhizome (Fig. S3):
(a) Rhizome radially symmetrical with a dense mantle of leaf bases and rootlets
(b) Siphonostele, ectophloic-dictyoxylic
(c) Pith parenchymatous
(d) Xylem cylinder thin (<15 tracheids thick), dissected by mostly complete leaf gaps
(e) Inner cortex thin, parenchymatous; outer cortex thick, homogeneous, fibrous
(f) Leaf traces endarch, initially oblong to slightly curved with one protoxylem cluster
(g) Adventitious roots arising singly from each leaf trace
(h) Stipe-base vascular strand C-shaped, enclosing a mass of thick-walled fibers in its
(i) Stipe-base sclerenchyma ring heterogeneous, containing thin- and thick-walled fibers
Following systematic treatments of Osmundaceae (1, 35),
(a, b) are diagnostic of family Osmundaceae,
(b, c) are diagnostic of subfamily Osmundoideae,
(df) are diagnostic of genus Osmunda s.l. and of the fossil form-genus Ashicaulis,
(h, i) are diagnostic of genus Osmunda s.l.,
and (g) is typical of subgenus Osmundastrum.
Fossils with overall comparable character combinations have been assigned to the form-
genus Ashicaulis [see (4, 5, 31–34)] or described as fossil representatives of Osmunda
(e.g., O. pluma, O. arnoldii, O. dowkeri, and fossil O. cinnamomea) (3). Preliminary
analyses indicate that the studied specimen shows a unique combination of specific
anatomical characters, and probably represents a new species.
X-ray fluorescence analysis:
In decreasing abundance, the most common elements detected in the volcaniclastic host
rock are Si (36.65%), Fe (26.8%), Al (16.6%), Mg (8.65%), K (6.77%), Ti (2.34%), and
Ca (1.47%) indicating a dominance of Fe-, Al- and Mg- silicate minerals in the mafic
volcaniclastic matrix (table S1). Other elements constitute < 1% of the rock composition
(table S1). Note that the XRF analyser does not detect elements with atomic numbers less
than that of Mg, so the registered percentages (table S1) are exclusive of those elements.
The composition of the host rock is thus consistent with that of the mafic alkaline
magmatic rocks of the central Skåne volcanic province (35). The results from the XRF
analysis of the fossil fern, by contrast, show an extremely high value of Ca (91.84%),
followed by Si (3.21%) and P (1.96%). The very different compositions of the fossil and
rock matrix demonstrate that calcite cement precipitated preferentially around and within
the entombed plant remains, which we infer to be a result of contrasting local porosity
and chemical environments within and around buried plant tissues.
Fig. S1.
Map of southern Sweden showing the location of the Korsaröd fossil site in the central
Skåne volcanic province.
Fig. S2
Light micrographs of representative fossil spores and pollen grains from the 'Djupadal
formation' at the Korsaröd locality; taxon, rock sample number, palynomorph specimen
number, and microscope X/Y calibration position.
(AC) Osmundacidites wellmanii Couper 1953; (A) NRM S069738, NRMS089691-01,
127/15; (B) NRM S069690, NRMS089687-01, 119/7; (C) NRM S069730,
NRMS089689-01, 144/17; (D) Stereisporites psilatus (Ross) Pflug in Thomson & Pflug
1953, NRM S069690, NRMS089687-02, 137/5; (E) Stereisporites seebergensis Schulz
1966, NRM S069730, NRMS089689-02, 132/10; (F) Retitriletes clavatoides Döring
1963, NRM S069690, NRMS089687-03, 134/5; (G) Retitriletes semimuris (Danze-
Corsin & Laveine 1963) McKellar 1974, NRM S069730, NRMS089689-03, 114/18;
(H) Cibotiumspora jurienensis (Balme) Filatoff 1975, NRM S069690, NRMS089687-04,
113/14; (I) Deltoidospora toralis (Leschik) Lund 1977, NRM S069730, NRMS089689-
04, 140/20; (J) Striatella seebergensis Mädler 1964, NRM S069690, NRMS089687-05,
132/10; (K) Marattisporites scabratus Couper 1958, NRM S069730, NRMS089689-05,
142/8; (L) Classopollis classoides (Pflug) Pocock & Jansonius 1961, NRM S069690,
NRMS089687-06, 125/15; (M) Vitreisporites pallidus (Reissinger) Nilsson 1958, NRM
S069738, NRMS089691-02, 124/16; (N) Chasmatosporites hians Nilsson 1958, NRM
S069730, NRMS089689-06, 139/18; (O) Chasmatosporites apertus (Rogalska) Nilsson
1958, NRM S069690, NRMS089687-07, 137/2; (P) Monosulcites punctatus Orlowska-
Zwolinska 1966, NRM S069730, NRMS089689-07, 133/8;
(Q) Eucommiidites troedssonii Erdtman 1948, NRM S069690, NRMS089687-08,
144/15; (R) Perinopollenites elatoides Couper 1958, NRM S069690, NRMS089687-09,
137/15. Scale bars 10 μm.
Fig. S3
Transmitted-light micrographs illustrating the diagnostic morphological and anatomical
features of the Korsaröd fern fossil. (A) Transverse section through the radially
symmetrical rhizome with a dense mantle of stipe bases and rootlets (a), NRM S069656;
(B) detail of transverse section through the stem showing the ectophloic-dictyoxylic
siphonostele (b), the parenchymatous pith (c), the thin xylem cylinder dissected by
complete gaps (d), the thin parenchymatous inner cortex and fibrous outer cortex (e), and
the single root per leaf trace (g), NRM S069656; (C) transverse section through an
endarch, slightly reniform leaf trace with a single protoxylem cluster (f) in the inner
cortex of the stem, NRM S069656; (D) transverse section through a stipe base showing
the C-shaped leaf trace and enclosed sclerenchyma mass (h) and an arch of thick-walled
fibers in the sclerenchyma ring (i), NRM S069657. Scale bars (A) 5 mm; (B, D) 500 µm;
(C) 50 µm.
Fig. S4
Morphological, anatomical, and cytological features of the Korsaröd fern fossil (AF)
compared to those of extant Osmunda regalis (G) and Osmundastrum cinnamomeum (H
L). (A, G) Gross morphology of rhizome showing dense mantle of persistent stipe bases
and fine roots; (B, H) stem cross sections showing the equivalent ectophloic-dictyoxylic
siphonostele; (C, I) longitudinal sections of stem portions showing xylem cylinder with
scalariform-pitted tracheids of the stele (left) and organelle-bearing parenchyma cells of
the pith (right); (D, J) details of three cortical parenchyma cells, each containing a
nucleus; (E, F, K, L) details of interphase nuclei with intact nuclear membranes and
prominent nucleoli. Images H and I used with kind permission of the Cornell University
Plant Anatomy Collection (CUPAC; Fossil specimens: (A)
reassembly of original fossil now cut into blocks NRM S069649–S069655; (B) thin
section S069656; (C) thin section NRM S069658; (DE) NRM S069656. (J–L) Thin
section of extant O. cinnamomeum, NRM S089694. Scale bars (A, G) 1 cm; (B, H) 500
μm; (C, I) 100 μm; (D–F, KL) 5 μm.
Fig. S5
Intracellular details of the Korsaröd fern fossil revealed through SEM of acid-etched
surfaces (AE) and through synchrotron X-ray tomographic microscopy of a stipe
portion (F, G). (A) Vascular-bundle tracheids (left), parenchyma cell walls, and
preserved nuclei projecting from etched surface of longitudinal section of a stipe, NRM
S069655; (B, C) details of etched longitudinal sections through a stipe showing
projecting nuclei (arrows in B), NRM S069655; (D, E) etched surface of a transverse
section of a stipe showing tracheid cells with characteristic scalariform pitting and an
associated parenchyma cell containing putative amyloplasts (arrows), NRM S069649; (F,
G) semi-translucent box reconstructions of small portions of cortical parenchyma in a
stipe showing distribution of nuclei, some with visible nucleoli (arrow in G; see movies
S1, S2), NRM S069654. Scale bars (A, B, D) 25 μm; (C, G) 10 μm; (E) 5 μm; (F) 50
Fig. S6
Signs of necrosis and programmed cell death in the Korsaröd fern fossil. (A) Radial
longitudinal section through the stem showing (from left to right) cortical tissues, xylem
cylinder, and pith, with a darker patch of apparently necrotic tissue in the inner cortex
(image center); (B) detail of the same, showing shrunken cytoplasm and pyknotic nuclei
(arrow) typical of apoptosis (36); (C, D) details showing pyknotic nuclei containing
homogeneous nuclear contents condensed into a distinctive dark crescent at one pole of
the former nuclear envelope. All images from NRM S069658. Scale bars (A) 500 µm;
(B) 40 µm; (C) 10 µm; (D) 5 µm.
Table S1
Results of X-ray fluorescence analysis of the volcaniclastic host rock and the fern fossil
from the Korsaröd site, showing the proportions of major (bold font), minor (regular font)
and trace (gray) elemental components.
Fern fossil
8 mm (ppm)
error (%)
8 mm (ppm)
error (%)
Movie S1
Conventional tomographic reconstruction of a cuboidal portion of stipe parenchyma from
the Korsaröd fern fossil showing cell walls and distribution of nuclei. Note nucleoli, e.g.,
within a nucleus in the upper left corner of the box after ca ¼ rotation.
Movie S2
Red-cyan stereoscopic tomographic reconstruction of the same.
References and Notes
1. W. Hewitson, Comparative morphology of the Osmundaceae. Ann. Mo. Bot. Gard. 49, 5793
(1962). doi:10.2307/2394741
2. C. Phipps, T. Taylor, E. Taylor, R. Cúneo, L. Boucher, X. Yao, Osmunda (Osmundaceae)
from the Triassic of Antarctica: An example of evolutionary stasis. Am. J. Bot. 85, 888
895 (1998). Medline doi:10.2307/2446424
3. C. N. Miller, Contrib. Mus. Paleontol. 23, 105169 (1971).
4. G. W. Rothwell, E. L. Taylor, T. N. Taylor, Ashicaulis woolfei n. sp.: Additional evidence for
the antiquity of osmundaceous ferns from the Triassic of Antarctica. Am. J. Bot. 89, 352
361 (2002). Medline doi:10.3732/ajb.89.2.352
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... В некоторых захоронениях встречены остатки Osmunda, которые редки или единичны. Представители этого рода впервые появляются в юрское время Евро-Синийской (Bomfleur et al. 2014) и Сибирской палеофлористических областей, и встречаются чаще в ранней и позднемеловой эпохах (Красилов 1979;Самылина 1976, 1988Vachrameev 1991). В изученных захоронениях с восточного побережья Уссурийского залива и в низовьях р. ...
A taxonomic study of Albian ferns from the Partizansk Coal Basin of Primorsky Krai was carried out. The Albian Age was an important stratigraphic milestone, when the Early Cretaceous flora changed to the Late Cretaceous flora. It was revealed that typical Mesozoic Onychiopsis predominated in taphocenoses, and representatives of young and evolutionarily advanced taxa Asplenium, Birisia appeared. The taxonomic composition of ferns in the Albian taphocenoses was almost constant from north to south. The vegetation of the Partizansk Basin occupied the coastal plain during Albian time, which was confirmed by the remains of marine and freshwater mollusks, phytofossils, as well as fish.
... Some of the early-diverged lineages (e.g., Osmundaceae) have shown relatively limited genome size (GS) range, chromosome diversity and low sequence substitution rates [6]. Indeed, the discovery of an extremely well preserved fossil featuring chromosomes and nuclei, showing clear affinities to extant relatives, led the authors to hypothesize that fern genomes have remained remarkably stable over time [7]. ...
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Giant genomes are rare across the plant kingdom and their study has focused almostexclusively on angiosperms and gymnosperms. The scarce genetic data that are available for ferns,however, indicate differences in their genome organization and a lower dynamism compared toother plant groups. Tmesipteris is a small genus of mainly epiphytic ferns that occur in Oceaniaand several Pacific Islands. So far, only two species with giant genomes have been reported inthe genus, T. tannensis (1C = 73.19 Gbp) and T. obliqua (1C = 147.29 Gbp). Low-coverage genomeskimming sequence data were generated in these two species and analyzed using the RepeatExplorer2pipeline to identify and quantify the repetitive DNA fraction of these genomes. We found that bothspecies share a similar genomic composition, with high repeat diversity compared to taxa withsmall (1C < 10 Gbp) genomes. We also found that, in general, characterized repetitive elementshave relatively high heterogeneity scores, indicating ancient diverging evolutionary trajectories.Our results suggest that a whole genome multiplication event, accumulation of repetitive elements,and recent activation of those repeats have all played a role in shaping these genomes. It will beinformative to compare these data in the future with data from the giant genome of the angiospermParis japonica, to determine if the structures observed here are an emergent property of massivegenomic inflation or derived from lineage specific processes.
... nigra and P. sylvestris) by obtaining empirical data. Abundant empirical evidence has been accumulated over time for all forms of evolution models (Campbell 1990;Erwin and Anstey, 1995;Futuyma 2005;McCarthy and Rubridge, 2005;Benton and David, 2009;Bomfleur et al. 2014). The great discussion between scientists has been about the credibility of the fossil record, intermediate forms (known as Darwin's dilemma) and morphogenesis (Wyles et al. 1983;Bromham et al. 1998Bromham et al. , 1999Bromham et al. , 2002Valentine et al. 1999;Smith and Peterson, 2002). ...
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Here, from macrophylogeographic mtDNA empirical data, we propose a scenario for the evolution and speciation of two important forest trees, European black pine and Scotch pine, and their multiple subspecies and varieties. Molecular clock simulations revealed that INDEL variability in the Pinus mitochondrial genome is relatively old, i.e., from the Pliocene-Miocene epoch, and related to historical tectonic continental fluctuations rather than to climate change at a large geographic scale. For conservation and management biodiversity program recommendations, special attention is given to the relationships between different speciation models, historical migration patterns, and differences between peripheral and central populations. Species evolution involves the mixing of different speciation modes, and every speciation mode has different effects on different DNA types (e.g., mitochondrial vs. chloroplast vs. nuclear DNA). The misbalance between the contributions of different meta-population census sizes vs. effective population sizes to asymmetric migration patterns is the result of different genotypes (and subphylogenetic lines) responding to selection pressure and adaptive evolution. We propose initial minimal size of conservation unit (between 3 and 5 ha) from central and marginal natural area of distribution for both species in the dynamic management system for practical forest genetic diversity management. The proposed physical sizes was determine by the effective population size, effective radius of seed distribution data, forest density age dynamics, succession pattern, natural selection pressing and species biology [R-17].
... This may be the reason for the high grade of preservation and the maintenance of the original anatomy down to cellular level. Similar examples of rapid permineralization preserving exceptionally delicate features, such as nuclei and starch grains of osmundaceous ferns and fungal hyphae, are known from hydrothermally influenced deposits of southern Sweden (Bomfleur et al. 2014;McLoughlin and Bomfleur 2016). It is likely that geothermal springs and associated groundwaters oversaturated by silica could have been of importance for the survival of these giant fungal growth structures. ...
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The enigmatic fossil Prototaxites found in successions ranging from the Middle Ordovician to the Upper Devonian was originally described as having conifer affinity. The current debate, however, suggests that they probably represent gigantic algal–fungal symbioses. Our re-investigation of permineralized Prototaxites specimens from two localities, the Heider quarry in Germany and the Bordeaux quarry in Canada, reveals striking anatomical similarities with modern fungal rhizomorphs Armillaria mellea. We analysed extant fungal rhizomorphs and fossil Prototaxites through light microscopy of their anatomy, Fourier transform infrared spectroscopy, X-ray microscopy, and Raman spectroscopy. Based on these comparisons, we interpret the Prototaxites as fungi. The detailed preservation of cell walls and possible organelles seen in transverse sections of Prototaxites reveal that fossilization initiated while the organism was alive, inhibiting the collapse of delicate cellular structures. Prototaxites has been interpreted to grow vertically by many previous workers. Here we propose an alternative view that Prototaxites represents a complex hyphal aggregation (rhizomorph) that may have grown horizontally similar to modern complex aggregated mycelial growth forms, such as cords and rhizomorphs. Their main function was possibly to redistribute water and nutrition from nutrient-rich to nutrient-poor areas facilitating the expansion for early land plant communities.
... nigra and P. sylvestris) by obtaining empirical data. Abundant empirical evidence has been accumulated over time for all forms of evolution models (Campbell 1990;Erwin and Anstey, 1995;Futuyma 2005;McCarthy and Rubridge, 2005;Benton and David, 2009;Bomfleur et al. 2014). The great discussion between scientists has been about the credibility of the fossil record, intermediate forms (known as Darwin's dilemma) and morphogenesis (Wyles et al. 1983;Bromham et al. 1998Bromham et al. , 1999Bromham et al. , 2002Valentine et al. 1999;Smith and Peterson, 2002). ...
Here, from macrophylogeographic mtDNA empirical data, we proposed a scenario of the evolution and speciation of two important forest trees, European Black Pine and Scotch Pine, and their multiple subspecies and varieties. Molecular clock simulations revealed that INDELs variability in the Pinus mitochondrial genome is relatively old, i.e., from the Pliocene-Miocene epoch, and related to historical tectonic continental fluctuations rather than climate change on a large geographic scale. Special attention is paid to the relationships between different speciation models and historical migration patterns and between peripheral and central populations. Species evolution involves the mixing of different speciation modes rather than only one of them, and one speciation mode has different results/effects on different DNA types (e.g., mitochondrial vs. chloroplast vs. nuclear DNA). The misbalance between different meta-population census size vs. effective population size contributions for asymmetric migration pattern is a result of different genotypes (and sub-phylogenetic lines) responding to selection pressing and adaptive evolution.
... In some cases, these woods have indifferent preservation. However, rare cases of rapid permineralization has resulted in spectacular preservation of anatomical details of fossil fern rhizomes (Fig. 2F) down to the level of cell organelles and chromosomes (Bomfleur et al. 2014, Such preservation has enabled both precise description of the fossil plants but also yielded greater insights into Osmundaceae phylogeny, diversification and plant-fungalanimal interactions , McLoughlin & Bomfleur 2016. ...
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Although its geology is dominated by pre-Cambrian crystalline rocks, Sweden’s palaeobotanical research output is substantial. Over 150 years of dedicated research has yielded several hundred papers on Sweden’s palaeobotanical and palynological heritage spanning much of the geological column. Studies have targeted all categories of plant and protest remains from Proterozoic microfossils to Quaternary woods, and marine microplankton to animal-plant interactions, and fossil microbes of the deep biosphere. Sweden is particularly renowned for its research on Proterozoic–Cambrian carbonaceous microfossils, Triassic-Jurassic floras, Santonian–Campanian (Late Cretaceous) charcoalified, mummified, adpression and permineralized angiosperms and gymnosperms, and Quaternary high-latitude spore-pollen records. Although a vast body of work has been carried out on these floras, there is great potential for further work on all these assemblages with regard to fossil plant systematics, biostratigraphy, biogeography, plant-animal-fungal interactions, and palaeoclimate/palaeoenvironmental research.
Surveys of the caterpillars of Area Conservacion de Guanacaste (ACG), northwestern Costa Rica, documented an array of litter moths (Erebidae: Herminiinae) feeding on ferns in at least 17 families. This represents the first documentation of extensive oligophagous fern-feeding among Herminiinae and possibly within New World Erebidae. Collectively, the taxonomic composition of foodplants of pteridivorous Herminiinae in ACG differs markedly from those of corresponding fern foodplants of sympatric Noctuidae: they are less concentrated in Polypodiales and tree ferns (Cyatheaceae) are among the primary foodplants of several herminiines. These have been recorded only rarely as foodplants of ACG noctuids. Pteridivorous herminiines also appear closely related to species variously recorded from dead leaves, algae, mosses (Bryophyta), spikemosses (Selaginaceae), palms (Arecaceae), and the exclusively New World family Cyclanthaceae. Feeding on monocots and mosses by caterpillars with pteridivorous congeners may even represent a more general pattern that is shared, for example, with certain sawflies (Tenthredinidae).
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Karyotype divergence may strongly affect the rate of hybridization between species in their secondary contact zones. Slow worms ( Anguis , Anguidae) are morphologically relatively cryptic legless lizards representing two evolutionary lineages, A. cephallonica from the southernmost Balkans, and the A. fragilis species complex (comprising two sister-species pairs A. fragilis + A. veronensis and A. colchica + A. graeca ) distributed in the Western Palearctic. To identify their level of chromosomal variation, we surveyed karyotype of all species except formerly studied A. veronensis and included Pseudopus apodus as an outgroup. We applied conventional and molecular cytogenetic methods and whole-chromosome painting using macrochromosome probes from Varanus komodoensis and interpreted the results within the evolutionary framework of the common clade Anguiformes. Unlike New World anguids with remarkable karyotype variation, all Anguis species and P. apodus have conserved diploid chromosome number 2 n = 44 (20 macrochromosomes, 24 microchromosomes) and morphology. The sister species A. colchica and A. graeca (divergence 4.4 Mya) displayed highly similar karyotype features within our sample. In contrast, despite the generally conserved chromosome morphology, the phylogenetically older A. cephallonica (divergence 12.0 Mya), and A. colchica versus A. fragilis (divergence 6.7 Mya) exhibited distinct patterns of constitutive heterochromatin distribution and telomeric repeat accumulation. The chromosome painting revealed that slow worm karyotype mostly evolved by fissions of ancestral macrochromosomes, which likely occurred already in an Anguis + Pseudopus common ancestor. Our findings thus demonstrate karyotype stasis in Anguis and Pseudopus for > 25 My, with fixed species-specific differences which may serve as cytotaxonomic markers useful in hybrid zone studies of slow worms.
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The Palaeobotany Department of the Swedish Museum of Natural History was established in the late 1800s and has supported research on a diverse range of plants of all ages. The Department hosts, manages, and regularly contributes additional material to, one of the largest fossil plant collections in Europe. The fossil collections have provided the basis for several thousand scientific publications by staff and visiting scientists over the course of its history. In addition to the work of its staff, the department has hosted many hundreds of visiting scientists over the past 140 years. It will continue to provide an invaluable resource for research on the evolution of plant and fungal life on Earth for long into the future. Now under the management of just its sixth administrative Head since 1884, the department is forging new pathways in palaeobotanical research utilizing cutting-edge technologies to provide advances in plant systematics, phylogeny, biogeography, biostratigraphy, palaeoenvironmental analysis, plant-animal interactions, and fossil fungal/microbial studies. The department is aware of multiple risks facing the survival of palaeontological collections in the 21st century and has put in place strategies to maintain access to and relevancy of the collections for future generations.
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Permineralized osmundaceous rhizome with anatomical and phylogenetic information plays a significant role in understanding the origin, evolution, and diversity variation of the fern family Osmundaceae in geological history. The northern Hebei and western Liaoning region is one of the most important fossil localities for the Jurassic osmundaceous rhizome fossils in the Northern Hemisphere; however, the diversity character of osmundaceous rhizome fossil remains poorly known. A new structurally preserved fern rhizome species, Ashicaulis wangii sp. nov., is described from the Middle Jurassic Tiaojishan Formation in Beipiao City, Liaoning Province, northeastern China. The rhizome is composed of heterogeneous pith, an ectophloic-dictyoxylic siphonostele, a two-layered cortex, and a mantle of adventitious roots and petiole bases. The xylem cylinder, with complete leaf gaps, consists of 15-17 xylem strands. The petiole base is characterized by a heterogeneous sclerotic ring and numerous sclerenchyma masses in the petiolar cortex. Among five known Ashicaulis species with heterogeneous sclerotic ring, four of them are documented from China. Therefore, osmundaceous rhizome fossils from China show endemic anatomical characteristics and significances for palaeobiogeography. Comparisons of anatomical features suggest that A. wangii sp. nov. bears close similarities to Osmunda pluma Miller from the Paleocene of Dakota, USA. Fossil species of A. wangii provides new evidence for further understanding the species diversity of osmundaceous rhizome fossil in China and in the Northern Hemisphere, and contributes to exploring the macroevolution process of the Mesozoic osmundaceous plants.
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A new species of structurally preserved fern rhizome, Ashicaulis plumites (Osmundaceae, Filicales), is described from the Middle Jurassic Tiaojishan Formation in western Liaoning Province, NE China. The new species is characterized by a peculiar sclerenchyma mass in the petiolar vascular bundle concavity. This sclerenchyma mass varies from a linear-shape to a mushroom-like shape with a remarkable outward protuberance, which distinguishes the present new species from other Ashicaulis species. Such a protuberance is very rare among osmundaceous ferns, and should represent a unique type for sclerenchymatous tissue in the osmundaceous vascular bundle concavity. Recognition of the peculiar structure of this new fossil species enriches anatomical diversity of permineralized osmundaceous ferns, indicating that the family Osmundaceae might have experienced a remarkable diversification during the Middle Jurassic in NE China. The new species show anatomical similarities to Osmunda pluma Miller from the Palaeocene of North America. The occurrence of A. plumites in the Middle Jurassic of China provides a new clue for understanding the evolution of some members of the living subgenus Osmunda.
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The mode of preservation dictates the preparation technique that will yield the most information about a specific fossil. Such considerations also include the time needed for preparation and degree of specimen destruction. Nowhere is this more clearly demonstrated than in the history of Carboniferous coal ball and chert research where the standard technique shifted from thin section to acetate peel preparations many years ago. Despite the ease and efficiency of acetate peels and the exponential increase in information they have provided about Carboniferous plants and ecosystems, we argue that there has been a concomitant decrease in attention directed at the microbial life also preserved in many cherts and coal balls. With this paper we endorse the use of thin sections, rather than peels, in order to study accurately the morphology and diversity of late Paleozoic microbial life.
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The strong positive relationship evident between cell and genome size in both animals and plants forms the basis of using the size of stomatal guard cells as a proxy to track changes in plant genome size through geological time. We report for the first time a taxonomic fine‐scale investigation into changes in stomatal guard‐cell length and use these data to infer changes in genome size through the evolutionary history of land plants. Our data suggest that many of the earliest land plants had exceptionally large genome sizes and that a predicted overall trend of increasing genome size within individual lineages through geological time is not supported. However, maximum genome size steadily increases from the M ississippian ( c . 360 million yr ago (Ma)) to the present. We hypothesise that the functional relationship between stomatal size, genome size and atmospheric CO 2 may contribute to the dichotomy reported between preferential extinction of neopolyploids and the prevalence of palaeopolyploidy observed in DNA sequence data of extant vascular plants.
A detailed study of the palynology and palynofacies of the Fjerritslev Formation (Lower Jurassic - basal Middle Jurassic) has resulted in the definition of four spore/pollen zones and four dinoflagellate cyst zones. The spore/pollen zones are the Corollina - Ricciisporites Zone (Late Rhaetian), the Cerebropollenites macroverrucosus Zone (Sinemurian - Pliensbachian), the Spheripollenites - Leptolepidites Zone (Toarcian), and the Perinopollenites elatoides Zone (Middle Jurassic). The dinoflagellate cyst zones are the Rhaetogonyaulax rhaetica Zone (Rhaetian), the Dapcodinium priscum Zone (latest Rhaetian - earliest Sinemurian), the Liasidium variabile Zone (Sinemurian), and the Nannoceratopsis gracilis Zone (Late Pliensbachian - ?Bajocian/Bathonian). These zones, and the Pinuspollenites - Trachysporites Zone Lund 1977 (Hettangian), are proposed for use in the Danish Subbasin. The combined spore/pollen and dinoflagellate cyst zonation has resulted in a detailed biostratigraphical subdivision of the sequences studied. A new combination, Manumia delcourtii (Pocock 1970) nov. comb. et emend., is proposed here, and the species description emended. New photographs of the holotypes of some of the species erected by Nilsson (1958) are included in the plates. The kerogen assemblages recorded from the Fjerritslev Formation, indicate a marine depositional environment, with a high but variable influence of terrestrially-derived organic particles. Stratigraphic variation in the kerogen assemblages generally correlate with the lithostratigraphical subdivision, and support previous environmental interpretations of the Fjerritslev Formation. Indications of strongly reducing conditions in the bottom waters were found in the Stenlille-2 borehole, in samples here referred to the Early Toarcian. The variations in the kerogen assemblages in the sequence investigated from the Gassum-1 borehole are not correlatable with the other boreholes, but seem primarily to reflect a distinct decrease in bioturbation in the Late Sinemurian. The Fjerritslev Formation does not generally represent a potential source rock for oil. Some levels (parts of the F-111 member) show, however, the characteristics of a fair to good source rock. The organic matter is generally immature or only at the earliest stage of maturity.
The mating system and the genetic system of the homosporous fern Osmunda regalis were investigated. Seven populations from western Massachusetts were sampled. All the sporophytes investigated were found to be heterozygous for zygotic lethals. Morphological studies of the gametophytes indicated an intergametophytic mating system when the gametophytes were spatially and chronologically situated to exchange male gametes. Genetic studies evidenced a genetic system based upon duplicate loci.
The historical development of the cell death concept is reviewed, with special attention to the origin of the terms necrosis, coagulation necrosis, autolysis, physiological cell death, programmed cell death, chromatolysis (the first name of apoptosis in 1914), karyorhexis, karyolysis, and cell suicide, of which there are three forms: by lysosomes, by free radicals, and by a genetic mechanism (apoptosis). Some of the typical features of apoptosis are discussed, such as budding (as opposed to blebbing and zeiosis) and the inflammatory response. For cell death not by apoptosis the most satisfactory term is accidental cell death. Necrosis is commonly used but it is not appropriate, because it does not indicate a form of cell death but refers to changes secondary to cell death by any mechanism, including apoptosis. Abundant data are available on one form of accidental cell death, namely ischemic cell death, which can be considered an entity of its own, caused by failure of the ionic pumps of the plasma membrane. Because ischemic cell death (in known models) is accompanied by swelling, the name oncosis is proposed for this condition. The term oncosis (derived from onkos, meaning swelling) was proposed in 1910 by von Reckling-hausen precisely to mean cell death with swelling. Oncosis leads to necrosis with karyolysis and stands in contrast to apoptosis, which leads to necrosis with karyorhexis and cell shrinkage.
The amount of DNA in the nucleus of a cell is commonly referred to as the genome size or C-value and people have been estimating this character in plants and animals for over 50 years. Today, with data available for over 7,000 species (Table 19.1), land plants (embryophytes) are the best studied of the major taxonomic groups of eukaryotes. This chapter provides an overview of what is currently known about the diversity of genome sizes encountered in land plant groups and considers how such diversity might have evolved. The chapter by Greilhuber and Leitch (2012, this volume) will discuss the impact of this diversity on plants in terms of how differences in genome size have an impact at all levels of complexity, from the nucleus to the whole organism. This chapter should also be read with reference to those by Weiss-Schneeweiss and Schneeweiss (2012, this volume) who explore intra- and inter-specific chromosome complexity across angiosperms, including polyploidy and dysploidy, Murray (2012, this volume) who discusses gymnosperm chromosomes, and Barker (2012, this volume) who considers the chromosomes of monilophytes and lycophytes.
Thirteen species of the Osmundaceae were compared in the following respects: gross morphology of the fronds, sporangial structure, epidermal structure, leaf base anatomy and rhizome morphology. The purpose of comparing rhizome structure was to try to find anatomical criteria by which species could be identified in section, thereby providing a tool for the paleobotanist for determining affinities of fossil species. Disposition of sclerenchyma in the leaf bases is the only reliable character for this purpose. It is suggested that any descriptions of new living species or monographic treatments of the family should include this character. The subgenus Plenasium is unique in having two protoxylem groups in the leaf traces while they are still attached to the stem. The origin of this character is thought to be relatively recent and may have been derived through the subgenus Osmunda. Figures in the literature indicate that previous work on Todea and Leptopteris employed small rhizomes. Further study on larger rhizomes of these two genera may indicate the evolutionary pathway by which the stele in the family has undergone reduction in size and number of xylem bundles. Walter Hewitson, Department of Biology, Parsons College, Fairfield, Iowa.