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![Figure 1. Morphology and anatomy of the Paleozoic seed plant Medullosa. A, Reconstruction of Medullosa thompsonii, from Andrews (1940), reprinted with permission. Because of the need to fit the drawing on one page, the fronds in this reconstruction are drawn as if the plant were wilting. For an alternative reconstruction, see Pfefferkorn et al. (1984). B, A cross-section of Medullosa sp. from the Harvard University Paleobotanical Collections, with important anatomical features labeled]()
![Figure 5. Conduit specific conductivity (Ksc) for Medullosa (asterisks), Cordaites (stars), and Pinus (open triangles) for given pit area resistivities (rp). Comparison is made with vesselless angiosperm and conifer tracheids with comparable diameters for the two coniferophytes, and for a eudicot vessel with comparable diameter to Medullosa. Bolded characters identify values used as per-taxon standard throughout the paper. Values for vesselless angiosperm tracheids, conifer tracheids, and a eudicot vessel are from Hacke et al. (2007). Vesselless angiosperm and conifer tracheid diameters are presented next to crosses and squares. Owing to the lack of data for vessels with diameters comparable to Medullosa, 142 μm vessel value is extrapolated from “67% optimum” line in their Figure 1B. Bolded value for MedullosaKsc yields 77% of total hydraulic resistance from pits; bolded value for Cordaites has 67% of hydraulic resistance in pits. Because tracheid resistivity is highly variable with respect to diameter, two values are shown for vesselless angiosperm and conifer tracheids]()
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![Medullosa trunk showing organ connections A) Terminal trunk portion with attached fronds, deposited in upside-down position of Facies 5.2–5.3 (KH0196). Scale bar 15 cm. B) Transverse section of the Medullosa stem shown in view A. Note the regular arrangement of the many vascular bundles in the pith. Scale bar 2.5 cm. C) Detail of view B showing circular to elliptical-shaped vascular bundles. The lowermost two bundles show lateral enlargement close to bifurcation. Scale bar 3 mm. D) Part of the frond attached to the Medullosa stem showing Alethopteris schneideri pinnae. Scale bar 2.5 cm. E) Detail of the pinnules, their alethopterid attachment to the pinna axis and venation.]()
![Figure 7. A histogram of conductivity in Paleozoic seed plants versus extant gymnosperms. Coniferophytes fall near the left wall of both histograms. In the Paleozoic, Lyginopteris and Callistophyton fall at intermediate values of conductivity, and Medullosa at the high end. In the lower plot, angiosperm vessels fall at high conductivity values and normally exceed values shown here. Medullosa overlaps with small angiosperm vessels.]()
![Figure 7. Conductance normalized to cross-sectional wall thickness (Ksp) in Medullosa and Pinus tracheids versus diameter and length. Contours show lines of equal conductance (Ksp) in m2/MPa·s, and boxes outline size ranges possible in extant plants (for Pinus) or the fossil record (for Medullosa). Conductance in medullosan tracheids always exceeds that of pine tracheids]()
![Anatomical diversity of medullosan seed ferns at the excavation. A) Transverse section of a Medullosa-like stem showing a small pith, limited secondary growth in centripetal direction but extended secondary growth in centrifugal direction (KH0286). Scale bar 2 cm. B) Detail of view A. There is probably no further vascular bundle inside the pith. Scale bar 2.5 mm. C) Transverse section of a Medullosa stellata f. lignosa stem showing small pith and extended secondary growth (KH0067). Scale bar 3 cm. D) Detail of view C showing small circular-shaped vascular bundles in the pith (arrow). Scale bar 2.5 mm. E) Transverse section of a Medullosa stellata stem showing a large pith with numerous vascular bundles surrounded by a woody ring (KH0056). Scale bar 3 cm. F) Detail of view E showing vascular bundles of different size in the pith. Scale bar 1 cm.]()
![Figure 2. A, Light micrograph of Medullosa sp. tracheid; scale bar is approximately 130 μm. B, Surface view of a torus-margo pit from Tsuga canadensis (Lancashire and Ennos 2002). C, Surface view of homogeneous pit membrane of Fraxinus (modified from Choat et al. 2006). D, Diagram of idealized water flow through tracheids, showing the location and simplified cross-sectional view of torus-margo and homogeneous pit membranes]()
![Figure 4. Pit area resistance for Cordaites, Medullosa, and three types of xylem from Hacke et al. (2007): conifer tracheids, vesselless angiosperm tracheids, and eudicot vessels. Ranges for the two fossil taxa represent sensitivity analyses, with Dpore increasing from 5 to 65 nm with a 1 nm step size. Horizontal lines represent medians, box ranges represent 25th through 75th percentile range, vertical lines represent 10th to 90th percentiles, and symbols are outliers. Black stars indicate values that matched expected proportions of wall and lumen resistances and were used to calibrate default values for α and rp when calculating conductance. The value used for Medullosa overlaps with vesselless angiosperms, and Cordaites overlaps with conifers]()
![Figure 6. Conduit specific conductivity (Ksc) in Medullosa, Pinus, and Cordaites tracheids versus diameter and length. Note differences in scales in the three graphs. Color (z-axis values) is consistent across the three plots]()
![Figure 8. Medullosa (thick line), Cordaites (dotted line), and Pinus (thin line) thickness-to-span ratios versus tracheid diameter. Ranges are based on tracheid diameters and thicknesses found in fossils and the literature (Bannan 1965; Greguss and Balkay 1972). The hashed zone is where given thickness-to-span ratios cause irreversible implosion at −2 MPa (from Hacke et al. 2001)]()
![Figure 3. Proportion of tracheid resistance from cell wall (pits) as a function of diameter and length. Proportion of resistance from tracheid lumen is the reciprocal of the data shown. For tracheids as large as those in Medullosa, most of the hydraulic resistance comes from pits. Black stars indicate proportions of wall resistance that were used as default values for the three taxa and were used to calibrate values for α and Dpore. Tracheid dimensions: Medullosa, 142 μm, 25 mm; Cordaites, 25 μm, 3.3 mm; and Pinus, 39 μm, 3.8 mm]()
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![The rate at which water can be conducted upward through the stem is related to conductivity of individual xylem elements (specific conductivity, or Ksp). The plot shows modeled Ksp for a variety of living and Paleozoic seed plants (data from Wilson and Knoll, 2010). Living gymnosperms (blue) have relatively small, thick-walled tracheids that conduct water at low rates, whereas angiosperms (red) commonly have vessels with a high Ksp. Pennsylvanian seed plants (black) include the conifer-like Cordaites, with low per tracheid conductivity, but also genera such as Lyginopteris, Callistophyton, and, especially, Medullosa, which had Ksp intermediate between those of modern gymnosperms and angiosperms. Indeed, the large, porous conducting cells of Medullosa had a specific conductivity matched only by vessel-bearing flowering plants.]()
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![Figure 5. Separate two-dimensional views of pit area resistance (rp) versus length and rp versus diameter. Note that Medullosa and Cordaites have relatively high pit area resistance values, whereas living conifers have low pit area resistance values.]()
![Figure 3. Images of tracheids from three Paleozoic seed plants. A, Longitudinal section of Cordaites wood showing pits (scale bar, 20 µm). B, Macerated tracheid from Medullosa (scale bar, 120 µm). C, Transverse section of xylem from Lyginopteris oldhamium (scale bar, 80 µm).]()
![Figure 8. A decision tree of how to decrease total xylem resistance. There are two ways to decrease resistance: by reducing resistance of the wall and/or the lumen. To reduce end-wall resistance, there are two methods: increasing individual porosity, through the development of the torus-margo pit, or by adding pit area, which appears to be common in Paleozoic seed plants. To reduce lumen resistance, plants have turned either to multicellularity, which is found in angiosperm vessels, or to enlarging individual xylem cells, which is found in Medullosa and certain other Paleozoic seed plants.]()
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Journal Article
Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
Journal: Paleobiology
Publisher: Paleontological Society
Published: 01 November 2008
Paleobiology (2008) 34 (4): 472–493.
...Jonathan P. Wilson; Andrew H. Knoll; N. Michele Holbrook; Charles R. Marshall Abstract Medullosa stands apart from most Paleozoic seed plants in its combination of large leaf area, complex vascular structure, and extremely large water-conducting cells. To investigate the hydraulic consequences...
FIGURES
| View All (8)
Journal Article
Sur un nouveau Medullosa du Stephanien de Rive-de-Gier
Publisher: Société Géologique de France
Published: 01 January 1951
Bulletin de la Société Géologique de France (1951) S6-I (7): 419–423.
...Edouard Boureau Abstract Describes remains of the plant Medullosa geriensis (previously named, but never hitherto described) from Stephanian (Carboniferous) deposits of the Rive-de-Gier area, France. It is the youngest known representative of the subgenus Anglorota. GeoRef, Copyright 2016...
Image
Figure 1. Morphology and anatomy of the Paleozoic seed plant Medullosa . ...
in Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
> Paleobiology
Published: 01 November 2008
Figure 1. Morphology and anatomy of the Paleozoic seed plant Medullosa . A, Reconstruction of Medullosa thompsonii , from Andrews (1940) , reprinted with permission. Because of the need to fit the drawing on one page, the fronds in this reconstruction are drawn as if the plant were wilting
Image
Figure 5. Conduit specific conductivity ( K sc ) for Medullosa (asteris...
in Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
> Paleobiology
Published: 01 November 2008
Figure 5. Conduit specific conductivity ( K sc ) for Medullosa (asterisks), Cordaites (stars), and Pinus (open triangles) for given pit area resistivities ( r p ). Comparison is made with vesselless angiosperm and conifer tracheids with comparable diameters for the two coniferophytes
Image
Table 1. Measurements of tracheid length and diameter for fossil Medullos...
in Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
> Paleobiology
Published: 01 November 2008
Table 1. Measurements of tracheid length and diameter for fossil Medullosa and Cordaites specimens. Mean, stan dard deviation, and maximum and minimum dimensions are given for six taxa. Because complete tracheid length in Medullosa is difficult to observe in thin section, the numbers
Image
Medullosa trunk showing organ connections A) Terminal trunk portion with at...
in A SNAPSHOT OF AN EARLY PERMIAN ECOSYSTEM PRESERVED BY EXPLOSIVE VOLCANISM: NEW RESULTS FROM THE CHEMNITZ PETRIFIED FOREST, GERMANY
> PALAIOS
Published: 01 November 2012
Figure 7 Medullosa trunk showing organ connections A) Terminal trunk portion with attached fronds, deposited in upside-down position of Facies 5.2–5.3 (KH0196). Scale bar 15 cm. B) Transverse section of the Medullosa stem shown in view A. Note the regular arrangement of the many vascular bundles
Image
Figure 7. A histogram of conductivity in Paleozoic seed plants versus exta...
in A physiologically explicit morphospace for tracheid-based water transport in modern and extinct seed plants
> Paleobiology
Published: 01 May 2010
Figure 7. A histogram of conductivity in Paleozoic seed plants versus extant gymnosperms. Coniferophytes fall near the left wall of both histograms. In the Paleozoic, Lyginopteris and Callistophyton fall at intermediate values of conductivity, and Medullosa at the high end. In the lower plot
Image
Figure 7. Conductance normalized to cross-sectional wall thickness ( K sp...
in Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
> Paleobiology
Published: 01 November 2008
Figure 7. Conductance normalized to cross-sectional wall thickness ( K sp ) in Medullosa and Pinus tracheids versus diameter and length. Contours show lines of equal conductance ( K sp ) in m 2 /MPa·s, and boxes outline size ranges possible in extant plants (for Pinus ) or the fossil record
Image
Anatomical diversity of medullosan seed ferns at the excavation. A) Transve...
in A SNAPSHOT OF AN EARLY PERMIAN ECOSYSTEM PRESERVED BY EXPLOSIVE VOLCANISM: NEW RESULTS FROM THE CHEMNITZ PETRIFIED FOREST, GERMANY
> PALAIOS
Published: 01 November 2012
Figure 8 Anatomical diversity of medullosan seed ferns at the excavation. A) Transverse section of a Medullosa-like stem showing a small pith, limited secondary growth in centripetal direction but extended secondary growth in centrifugal direction (KH0286). Scale bar 2 cm. B) Detail of view
Image
Figure 2. A, Light micrograph of Medullosa sp. tracheid; scale bar is ap...
in Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
> Paleobiology
Published: 01 November 2008
Figure 2. A, Light micrograph of Medullosa sp. tracheid; scale bar is approximately 130 μm. B, Surface view of a torus-margo pit from Tsuga canadensis ( Lancashire and Ennos 2002 ). C, Surface view of homogeneous pit membrane of Fraxinus (modified from Choat et al. 2006 ). D, Diagram
Image
Figure 4. Pit area resistance for Cordaites , Medullosa , and three type...
in Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
> Paleobiology
Published: 01 November 2008
Figure 4. Pit area resistance for Cordaites , Medullosa , and three types of xylem from Hacke et al. (2007) : conifer tracheids, vesselless angiosperm tracheids, and eudicot vessels. Ranges for the two fossil taxa represent sensitivity analyses, with D pore increasing from 5 to 65 nm
Image
Figure 6. Conduit specific conductivity ( K sc ) in Medullosa , Pinus ,...
in Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
> Paleobiology
Published: 01 November 2008
Figure 6. Conduit specific conductivity ( K sc ) in Medullosa , Pinus , and Cordaites tracheids versus diameter and length. Note differences in scales in the three graphs. Color (z-axis values) is consistent across the three plots
Image
Figure 8. Medullosa (thick line), Cordaites (dotted line), and Pinus ...
in Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
> Paleobiology
Published: 01 November 2008
Figure 8. Medullosa (thick line), Cordaites (dotted line), and Pinus (thin line) thickness-to-span ratios versus tracheid diameter. Ranges are based on tracheid diameters and thicknesses found in fossils and the literature ( Bannan 1965 ; Greguss and Balkay 1972 ). The hashed zone is where
Image
Figure 3. Proportion of tracheid resistance from cell wall (pits) as a fun...
in Modeling fluid flow in Medullosa , an anatomically unusual Carboniferous seed plant
> Paleobiology
Published: 01 November 2008
Figure 3. Proportion of tracheid resistance from cell wall (pits) as a function of diameter and length. Proportion of resistance from tracheid lumen is the reciprocal of the data shown. For tracheids as large as those in Medullosa , most of the hydraulic resistance comes from pits. Black stars
Journal Article
A physiologically explicit morphospace for tracheid-based water transport in modern and extinct seed plants
Journal: Paleobiology
Publisher: Paleontological Society
Published: 01 May 2010
Paleobiology (2010) 36 (2): 335–355.
...Figure 7. A histogram of conductivity in Paleozoic seed plants versus extant gymnosperms. Coniferophytes fall near the left wall of both histograms. In the Paleozoic, Lyginopteris and Callistophyton fall at intermediate values of conductivity, and Medullosa at the high end. In the lower plot...
FIGURES
| View All (8)
Image
The rate at which water can be conducted upward through the stem is related...
Published: 01 January 2013
, Callistophyton , and, especially, Medullosa , which had K sp intermediate between those of modern gymnosperms and angiosperms. Indeed, the large, porous conducting cells of Medullosa had a specific conductivity matched only by vessel-bearing flowering plants.
Journal Article
A SNAPSHOT OF AN EARLY PERMIAN ECOSYSTEM PRESERVED BY EXPLOSIVE VOLCANISM: NEW RESULTS FROM THE CHEMNITZ PETRIFIED FOREST, GERMANY
Journal: PALAIOS
Publisher: SEPM Society for Sedimentary Geology
Published: 01 November 2012
PALAIOS (2012) 27 (11): 814–834.
...Figure 7 Medullosa trunk showing organ connections A) Terminal trunk portion with attached fronds, deposited in upside-down position of Facies 5.2–5.3 (KH0196). Scale bar 15 cm. B) Transverse section of the Medullosa stem shown in view A. Note the regular arrangement of the many vascular bundles...
FIGURES
| View All (12)
Image
Figure 5. Separate two-dimensional views of pit area resistance (r p ) ver...
in A physiologically explicit morphospace for tracheid-based water transport in modern and extinct seed plants
> Paleobiology
Published: 01 May 2010
Figure 5. Separate two-dimensional views of pit area resistance (r p ) versus length and r p versus diameter. Note that Medullosa and Cordaites have relatively high pit area resistance values, whereas living conifers have low pit area resistance values.
Image
Figure 3. Images of tracheids from three Paleozoic seed plants. A, Longitu...
in A physiologically explicit morphospace for tracheid-based water transport in modern and extinct seed plants
> Paleobiology
Published: 01 May 2010
Figure 3. Images of tracheids from three Paleozoic seed plants. A, Longitudinal section of Cordaites wood showing pits (scale bar, 20 µm). B, Macerated tracheid from Medullosa (scale bar, 120 µm). C, Transverse section of xylem from Lyginopteris oldhamium (scale bar, 80 µm).
Image
Figure 8. A decision tree of how to decrease total xylem resistance. There...
in A physiologically explicit morphospace for tracheid-based water transport in modern and extinct seed plants
> Paleobiology
Published: 01 May 2010
, or by adding pit area, which appears to be common in Paleozoic seed plants. To reduce lumen resistance, plants have turned either to multicellularity, which is found in angiosperm vessels, or to enlarging individual xylem cells, which is found in Medullosa and certain other Paleozoic seed plants.
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