Figure 2. Xylem cross-sectional area (CSAX) plotted against xylem perimeter (XP). Full circles = Rhynia data points, crosses = Asteroxylon data points. A, Rhynia, uncorrected data. The relationship between XP and CSAX for a model cylinder with a circular cross-section is included

Figure 4. cf. Xenocladia , Frasnian from El Gara. (a) General view of the decorticated axis showing multiple vascular strands, transverse section. GA5A1. × 3.7. (b) Detail of preceeding view. GA5A1. × 7.6. (c) Detail of a vascular strand showing an elongate core of primary xylem surrounded

Fig. 3. Sigillaria steles exhibit a coronal outer margin of the primary xylem. ( a – c ) Specimen 0069, palaeobotanical collections, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China, showing Sigillaria sp., probably S. pfefferkornii or S. wudensis

Figure 14. Secondary xylem deformation by compressed wood. ( 1 ) TS, “shearing zones;” ( 2, 4 ) TS, “s-shaped linear rows;” ( 3 ) TS, rays with an evident zig-zag pattern; ( 5, 6 ) TS, compressed wood in different directions; ( 7–9 ) RLS, hyphae simple or dichotomous; (9–11 ) RLS, hyphae

Fig. 4 BSE/SEM (A, C, E–H), and HR-CL/SEM images (B, D). A - secondary xylem porous in parts, “a false growth ring” due to undulation of tracheids; B - leached (whitish) part of wood with highly luminescing tracheid cell walls, dark cell lumina; C - agate-like textures within wood, iron oxide

Fig. 11. Difference in pressure head between root xylem and root surface, Δ h 0-xylem (m), calculated by Eq. [ 21 ] as a function of time and depth for simulations using the SWAP model with the de Jong van Lier reduction function, SWAP–DRF (fitting constant c in Eq. [ 14 ] = 3 and wilting

Figure 1. Model of water transport through xylem cells with morphospace dimensions highlighted: tracheid diameter (D tracheid ), tracheid length (L tracheid ), and end-wall resistance (R wall ). Water enters a cell through a series of apertures on the wall, called pits, flows through the lumen

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

Figure 4. Detail of triarch root with secondary xylem (University of San Juan, PBSJ 460a). Scale bar: 0.5mm

Fig. 4 Anatomical features seen in branch wood of Pitus primaeva at Montford, Isle of Bute. All images from BRSUG28886. ( A ) Pith and surrounding xylem, scale: 2 mm, TS; ( B ) Transition from parenchymatous pith (bottom) to periderm (top). Note the presence of growth interruptions in the xylem

F ig . 9. Xylem water potential ( h ) as function of rooting depth, without conductivity drop (dashed line) and with conductivity drop (solid line). The low radial conductivity ( L r *) scenario is denoted by the blue lines, the higher L r * scenario by the red lines.

F ig . 2. (a) Root architecture and initial water potential distribution; (b) xylem water potential after 5 d for Collar Boundary Condition 2; (c) soil water potential distribution after 5 d, white arrows show water streamlines; (d) soil water content distribution; and (e) sink term distribution.

Table 2 —Microprobe analysis for 13 elements in a xylem fragment exposed on the surface of a polished thin section prepared from coprolite specimen MOR 1130. The amounts of Fe, Mn, Ca, Sr, Al, Mg, S, K, P, C, and Ba are expressed as the weight percent of their respective oxides. Mean values were

FIGURE 9 —Thin section of conifer xylem fragment in coprolite specimen MOR 1131 before (A) and after (B) removal of calcite by EDTA solution under conditions of laminar flow at room temperature. Dark capillaries are viewed largely in oblique orientation. Scale bars are 100 μm

Figure 3. Xylem perimeter (XP) plotted against axis perimeter (AP). Full circles = Rhynia data points, crosses = Asteroxylon data points. A, Rhynia, uncorrected data. Regression: y = 0.086 x + 0.389; r 2 = 0.54. Uncorrected Asteroxylon data points fitting into the graph are included

Figure 4. Ratio of xylem perimeter to axis perimeter (PXP) plotted against axis diameter (AD) for both Rhynia and Asteroxylon, uncorrected data. Full circles = Rhynia data points, crosses = Asteroxylon data points

Figure 5. Cross-sectional area of xylem (CSAX) plotted against axis perimeter (AP) for both Rhynia and Asteroxylon, uncorrected data. Full circles = Rhynia data points, crosses = Asteroxylon data points

Figure 6. Xylem cross-sectional area (CSAX) plotted against cross-sectional area of parenchyma (CSAP). Full circles = Rhynia data points, crosses = Asteroxylon data points. A, Rhynia, uncorrected data. Uncorrected Asteroxylon data points fitting into the graph are included. B, Rhynia

Figure 7. Ratio of xylem to outer parenchyma cross-sectional area (RXOP) plotted against axis diameter (AD) for both Rhynia and Asteroxylon, uncorrected data. Full circles = Rhynia data points, crosses = Asteroxylon data points