. Fossil plants : for students of botany and geology . Paleobotany. X] CALLUS WOOD. 319 node. The mottled or watered appearance of the wood is due to numerous medullary rays which sweep across the tracheids.' The /â â â â <â â «N5''=-i'ivv'w4iiMaKi««^. Fig. 79. Longitudinal section of the specimen stem in fig. 78. From a specimen in the Williamson Collection, British Museum (no. 80). f nat. size. periderm elements, as seen in longitudinal section, are fibrous in form. The development of cork in a younger Calamite stem is clearly shown in a specimen described by Williamson and Scott in th
. Fossil plants : for students of botany and geology . Paleobotany. X] CALLUS WOOD. 319 node. The mottled or watered appearance of the wood is due to numerous medullary rays which sweep across the tracheids.' The /â â â â <â â «N5''=-i'ivv'w4iiMaKi««^. Fig. 79. Longitudinal section of the specimen stem in fig. 78. From a specimen in the Williamson Collection, British Museum (no. 80). f nat. size. periderm elements, as seen in longitudinal section, are fibrous in form. The development of cork in a younger Calamite stem is clearly shown in a specimen described by Williamson and Scott in their Memoir of 1894. In a transverse section of the stem several large cells of the inner cortex are seen to be in process of division by tangential walls, and giving rise to radially arranged periderm tissue ^- The section diagrammatically sketched in fig. 80 is that of a Calamite twig in which the wood appears to have been injured, and the wound has been almost covered over by the formation of callus wood. The young trees in a Palaeozoic forest might easily be injured by some of the large amphibians, which were the highest representatives of animal life during the Carboni- ferous period, just as our forest trees are often barked by deer, rabbits, and other animals. Fissures might also be formed by the expansion of the bark under the heating influence of the sun's rays^. Such a specimen as that of fig. 80 gives an air of living reality to the petrified fragments of the Coal period trees. 1 Williamson and Scott (94), p. 888. 2 Hartig (94), pp. 149, 297, 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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