. Fossil plants : for students of botany and geology . Paleobotany. 182 RHETINANGIEAE [CH. from the peripheral region of the primary xylem go to form a single leaf-trace: these U-shaped strands of xylem destined for a leaf are connected laterally by parenchyma and form an irregu- larly corrugated band. Fig. 450 shows a petiole-trace still enclosed on each side by the secondary xylem cylinder x^.. Fig. 449. Rhetinangium Arberi Gord. Transverse section of stem with large leaf-base; cr, outer cortex of stem; p, petiole. (After Gordon; x ] J.) There are several protoxylem groups in a leaf-trace, o
. Fossil plants : for students of botany and geology . Paleobotany. 182 RHETINANGIEAE [CH. from the peripheral region of the primary xylem go to form a single leaf-trace: these U-shaped strands of xylem destined for a leaf are connected laterally by parenchyma and form an irregu- larly corrugated band. Fig. 450 shows a petiole-trace still enclosed on each side by the secondary xylem cylinder x^.. Fig. 449. Rhetinangium Arberi Gord. Transverse section of stem with large leaf-base; cr, outer cortex of stem; p, petiole. (After Gordon; x ] J.) There are several protoxylem groups in a leaf-trace, one on the outer face of each xylem-strand. In the petiole the xylem groups are more intimately connected and the trace has the form of a flat band with abaxial protoxylem. There is no indication that a leaf-trace undergoes division into separate strands. The roots are described as tetrarch with well-developed secondary Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Seward, A. C. (Albert Charles), 1863-1941. Cambridge : University Press
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