. Fossil plants : for students of botany and geology . Paleobotany. 152 LYCOPODIALES [CH. Lepidodendron shoot. This applies to other species of the genus as well as to L. fuliginosum. Fig. 171, A, shows more clearly the broad zone of secondary parenchyma with the thinner-walled cambial region, a; the latter is represented on a larger scale in fig. 171, B. The section shown in fig. 168, D, and in fig. 170, A, affords an example of a stem in which the secondary tissue consists largely of narrow scalariform tracheae, x^; the primary stele has a diameter of 1 cm.; the secondary xylem, cc'^, forms
. Fossil plants : for students of botany and geology . Paleobotany. 152 LYCOPODIALES [CH. Lepidodendron shoot. This applies to other species of the genus as well as to L. fuliginosum. Fig. 171, A, shows more clearly the broad zone of secondary parenchyma with the thinner-walled cambial region, a; the latter is represented on a larger scale in fig. 171, B. The section shown in fig. 168, D, and in fig. 170, A, affords an example of a stem in which the secondary tissue consists largely of narrow scalariform tracheae, x^; the primary stele has a diameter of 1 cm.; the secondary xylem, cc'^, forms a fairly broad zone of parenchyma and tracheal elements through which leaf-traces pass vertically, a fact of some interest in comparison with the //—. Fio. 172. Lepidodendron fuliginosum. From a section (4x3-4 cm.) in the Williamson Collection, British Museum (No. 379), figured by Williamson, Phil. Trans. R. Soc. 1881, PI. 52. horizontal course which they pursue through the medullary rays in the normal secondary wood of L. vasculare and L. Wilnschi- anum. The secondary tracheae pass gradually into thin-walled cambial cells (a, fig. 168, D; 170, A) with parallel tangential walls. Fig. 171, C, shows the sinuous course of the secondary tracheae as seen in longitudinal section, and a few small groups of parenchymatous cells, mr, which may be of the nature of medullary rays, enclosed between the winding scalariform tracheae. The secretory zone of Lepidodendron fuliginosum agrees essentially with that of other species; it usually presents the. 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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