. The testimony of the rocks; . atop, year after year, a higherand yet. higher coronal of fronds. And in order to impartthe necessary strength to this trunk, and to enable it to warfor ages with the elements, its mass of soft cellular tissueis strengthened all round by ii^temal buttresses of densevascular fibre, tough and elastic as the strongest woods. the circumference; /, v, darkly-colored WQody fibres of great strength, the internal buttresses of the illustration; e, the outer cortical portionformed by the bases of the 62 THE PAL^ONTOLOGICAL Now, not a few of the more anomalous fo
. The testimony of the rocks; . atop, year after year, a higherand yet. higher coronal of fronds. And in order to impartthe necessary strength to this trunk, and to enable it to warfor ages with the elements, its mass of soft cellular tissueis strengthened all round by ii^temal buttresses of densevascular fibre, tough and elastic as the strongest woods. the circumference; /, v, darkly-colored WQody fibres of great strength, the internal buttresses of the illustration; e, the outer cortical portionformed by the bases of the 62 THE PAL^ONTOLOGICAL Now, not a few of the more anomalous forms of the CoalMeasures seem to be simply fern allies of the types Lycopo-dacege, Marsileaceae, arid Equisetum, that, escaping from themediocrity of mere herbs, shot up into trees, — some ofthem very great trees,—and that had of necessity to befurnished with a tissue widely different from that of theirminuter contemporaries and successors. It was of courseftn absolute mechanical necessity, that if they were to pre- Fig. Fig. 25, LEPIDODENDRON STERNBERGII.* * Fig. 23, Branching stem, with hark and leaves. Fig. 24, Extremity ofbranch. Fig. 25, Extremity of another branch, with indication of cone-like receptacle of spores or seed. HISTORY OF PLANTS. 63 sent, by being tall and large, a wide front to the tempest,they should also be comparatively solid and strong to resistit; but ^dth this simple mechanical requirement there seemsto have mingled a principle of a more occult character. TheGymnogens or conifers vrere the highest vegetable exist-ences of the period,—its true trees; and aU the tree-likefern allies were strengthened to meet the necessities oftheir increased size, on, if I may so speak, a coniferousprinciple. Tissue resembUng that of their contemporaryconifers imparted the necessary rigidity to their frame-work; nay, so strangely were they pervaded throughoutby the coniferous characteristics, that it seems difficult todetermine whether they really most resembled
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