Elements of geology, or, The Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments elementsofgeolog00lyel Year: 1868 Ch. XXIV.] CONIFERS OF THE COAL PERIOD. 477 or partial absorption of the original medullary axis (see figs. 531 and 532). This peculiar type of pith is observed in living plants of very different families, such as the common Walnut and the White Jas- mine, in which the pith becomes so reduced as simply to form a thin lining of the medullary cavity, across which transverse plates of pith extend horizontally, so as to
Elements of geology, or, The Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments elementsofgeolog00lyel Year: 1868 Ch. XXIV.] CONIFERS OF THE COAL PERIOD. 477 or partial absorption of the original medullary axis (see figs. 531 and 532). This peculiar type of pith is observed in living plants of very different families, such as the common Walnut and the White Jas- mine, in which the pith becomes so reduced as simply to form a thin lining of the medullary cavity, across which transverse plates of pith extend horizontally, so as to divide the cylindrical hollow into discoid interspaces. When these interspaces have been filled up with inorganic matter, they constitute an axis to which, before their true nature was known, the provisional name of Sternbergia (d, d, fig. 531) was given. In the above specimen the structure of the wood (6, figs. 531 and 532) is coniferous, and the fossil is referable to Endlicher's fossil genus Dadoxylon. The fossil named Trigonocarpon (figs. 553 and 554), formerly sup- posed to be the fruit of a palm, may now, according to Dr. Hooker, be referred, like the Sternbergia, to the Coniferce. Its geological im- portance is great, for so abundant is it in the Coal-Measures, that in certain localities the fruit of some species may be procured by the bushel; nor is there auy part of the formation where they do not occur, except the underclays and limestone. The sandstone, iron- stone, shales, and coal itself, all contain them. Mr. Binney has at length found in the clay-ironstone at Lancashire several specimens dis- playing structure, and from these, says Dr. Hooker, we learn that the Trigonccarpon belonged to that large section of existing coniferous plants which bear fleshy solitary fruits, and not cones. It resembled very closely the fruit of the Chinese genus Salisburia, one of the Yew tribe, or Taxoid conifers. In five of the fossil specimens there is evi- Fig. 534. Fig. 533. T
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