. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. GENERAL MORPHOLOGY 305 at Mariemont in Belgium, are about to be described by Mr. Kidston: to him I am indebted for the information that this large Lycopod bore its sporangia associated with the leaves of certain portions of the stem, without any cone-formation, or alteration of the form or disposition of the leaves which bear them: the fertile and sterile portions are distinguished only by the presence or absence of sporangia. It is, in fact, a typical repre- sentative of the " Selago" type,
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. GENERAL MORPHOLOGY 305 at Mariemont in Belgium, are about to be described by Mr. Kidston: to him I am indebted for the information that this large Lycopod bore its sporangia associated with the leaves of certain portions of the stem, without any cone-formation, or alteration of the form or disposition of the leaves which bear them: the fertile and sterile portions are distinguished only by the presence or absence of sporangia. It is, in fact, a typical repre- sentative of the " Selago" type, but of dendroid dimensions. In this connection it is interesting to note that Solms Laubach mentions certain " remains of great size, remarkable for the unusual thickness of the axis — classed by Lesquereux with Lepidophloios. Weiss also has described a similarly colossal cone as Lomatophloios macrolepidotus, but, unfortunately,. Sp. W. Fig 153. LepidoUrobus. Diagram showing axis and sporophylls in radial section. <z=axis of strobilus ; J=sporophylls and sporangia; *=stele ; z, c=inner cortex; m, c=mlddle cortex ; a, c=outer cortex ; / = pedicel; &=lainina of sporophyll; #=ligule ; I, <=leaf- trace; sp, i»=wall of sporangium, (Enlarged after Maslen, from Scott, Studies in Fossil Botany?) there is no detailed account of it. The enormous size of the axis in these specimens gives rise to the suspicion that the fructification was not confined to special fertile shoots, but might occasionally appear on the leaves even of the main stem, which then increased in thickness, much as we see in the present day in the female flower of Cycas, and mutatis mutandis in Lycopodium Selago. We naturally ask, on what sort of scars could such cones be seated as lateral organs?"1 Kidston's description of Pinakodendron shows that the "Selago" condition did actually exist in dendroid types, and thus resolves the difficulty. A similar condition is shown by the small Lyc
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