. Elements of geology : a text-book for colleges and for the general reader. Geology. PLAXTS OF THE COAL. 367 found in great abundance, and known under the name of Lepidostrobus (scale - cone), has shown that they bear in the axils of their scales spores like club - mosses, and not seeds like coni- fers. Also, like club-moss- es, there are in these plants two kinds of spores* —microspores and macro- spores. This would again ally them with conifers, for these organs may be said to represent the sta- mens and pistils of higher plants (Fig. 497). The ex- ternal appearance and in- florescence, the
. Elements of geology : a text-book for colleges and for the general reader. Geology. PLAXTS OF THE COAL. 367 found in great abundance, and known under the name of Lepidostrobus (scale - cone), has shown that they bear in the axils of their scales spores like club - mosses, and not seeds like coni- fers. Also, like club-moss- es, there are in these plants two kinds of spores* —microspores and macro- spores. This would again ally them with conifers, for these organs may be said to represent the sta- mens and pistils of higher plants (Fig. 497). The ex- ternal appearance and in- florescence, therefore, in- dicate that they are Lyco- pods, with very strong coniferous affinities. This conclusion is en- tirely borne out by the internal structure. Fig. 498 represents an ideal cross and longitudinal sec- tion of the stem of a Lep- idodendron. It is seen that the stem consists of a dense outer bark or rind, inclosing a great mass of loose cellular tissue or in- ner bark, through the center of which runs a comparatively small fibro- vascular cylinder, with very distinct pith. Bundles go from the cylin- der outward to form the venation of the leaves. Xow, the structure of a club-moss is almost the same, except that the fibro-vascular cylinder is solid, and there is, therefore, no pith. The presence in Lepidodendron of a dis- tinct pith is an important character, placing it far above modern Lycopods, and allying it most decidedly with Ex- ogens. Fig. -Lepidodendron compared with Club-Moss: a. club- moss; b, b'. scales enlarged; c, microspores; d, macro- spores; a1, lepidostrobus; y and z, the scales containing spores; m, microspores; n, macrospores (after Balfour).. 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 LeConte, Joseph, 1823-1901. New York : D. Appleton and Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1892
