Coal; its history and uses . Fig. 10. Transverse section of stem of Selagiuella ( x 150). From Sachs Botany. herbaceous forms of the same type; it indicates the ex-tent to v?hich physiological adaptation may mask realaffinity. The fruit of Lepidodendrou (often called Lepidostrobus)is more important than any other part of the plant forsystematic purposes. It has a somewhat cylindrical form,but is rounded above and below. Externally it is denselycovered with overlapping scales, which are merely leavesslightly modified. The internal structure of a Lepidos- H 2 100 COAL. trobus will be best unders
Coal; its history and uses . Fig. 10. Transverse section of stem of Selagiuella ( x 150). From Sachs Botany. herbaceous forms of the same type; it indicates the ex-tent to v?hich physiological adaptation may mask realaffinity. The fruit of Lepidodendrou (often called Lepidostrobus)is more important than any other part of the plant forsystematic purposes. It has a somewhat cylindrical form,but is rounded above and below. Externally it is denselycovered with overlapping scales, which are merely leavesslightly modified. The internal structure of a Lepidos- H 2 100 COAL. trobus will be best understood by comparison with thethe corresponding part of a recent club-moss. In Lycopodium certain leaves support at their basessporangia or spore-cases. These fertile leaves usuallydiffer in form from the ordinary foliage ; though in one. Fig. 11. Selaginella. A, fertile branch (one-half natural size). B, apex inlongitudinal section, bearing microspores on the left, and macrosporeson the right (magnified). From Sachs Botany. English species (Lycopodium Selago) they are nearlyuniform with them, and the upper part of the spike,which bears sporangia, is in this species hardly distin-guishable in outward appearance from the rest. In ourother Lycopodiums the fertile leaves are clustered together COAL PLANTS. 101 into separate cones, whicli differ from the sterile branchesin shape and size (resembling thus the fossil Lepidostro-bus), and also in colour. If one of these fertile Lycopo-dium cones be cut through vertically, the sporangia areseen nestling in the axils of the leaves, one at the base of
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherlo, booksubjectcoal
