Abstract
M. RENAULT has recently published a memoir, in which he reproduces the views of M. Brongniart respecting the relations which the Lepidodendra bear to the Sigillariæ, still insisting that the former are cryptogamic Lycopods, whilst the latter are exogenous Gymnosperms. In endeavouring to establish this position, the French palseo-botanist concludes that if the exogenous Diploxyloid stems (i.e., Sigillarian ones) are but matured states of some Lepidodendra, every Sigillarian type of organisation ought to be found in a young or Lepidodendroid form, because, he contends, the type of the central organisation, once established, undergoes no further change with advancing age. In support of his position he affirms that there are three such Sigillarian types, viz. (1) Sigillaria vascularis, (2) Diploxyloid stems, (3) Favularia and Leiodermaria. At present he contends that only the second of these forms has been discovered in Lepidodendron Harcourtii. He further believes that there are three types of Lepidodendron known, represented by (1) L. rhodumense, with a solid central vascular axis, in which the vessels are not intermingled with medullary cells; (2) by L. Harcourtii, in which the vascular axis is a cylinder surrounding a cellular medulla; and (3) an undescribed plant, which he names L. Jutieri, in which the vascular cylinder is broken up into detached bundles of vessels.
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Plants of the Coal-Measures 1 . Nature 22, 281–282 (1880). https://doi.org/10.1038/022281a0
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DOI: https://doi.org/10.1038/022281a0