Lepidostrobus is a genus that was established by Brongniart for Palaeozoic lycopod cones. Since then the genus has been used for a variety of cones that have similar characters. There is now compelling evidence that the genus represents a heterogeneous group of monosporangiate and bisporangiate cone species and that it should be divided. Lepidostrobus is rediagnosed as a genus of microsporangiate cones. Ftemingites Carruthers is rediagnosed as a genus of those bisporangiate cones formerly included in Lepidostrobus.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. International Association for Plant Taxonomy (IAPT) is collaborating with JSTOR to digitize, preserve and extend access to Taxon. IntroductionDissatisfaction with the current method of grouping fossil plants into families has grown out of our increased awareness of whole plant biology and recent emphasis on palaeoenvironments. Palaeobiologists are now bringing to life ancient environments that, although populated with vastly different plants than are present today, share many characteristics with present day habitats. There were in the Carboniferous swamps, for instance, trees, shrubs and herbaceous plants that appear to belong to very closely related groups, perhaps even families of plants. A parallel situation among today's environments that are dominated by angiosperms might, for instance, include an assemblage of plants that belong to the Fabaceae, Rosaceae or Cardiocarpaceae with each exhibiting very broad ranges of growth habits. The diversity of plants within these families is, however, recognized because genera of the families are united by their reproductive morphology rather than vegetative structure. This basic system that Linnaeus established has proven to be a successful method of grouping living plants regardless of overall vegetative morphology. Why not, then, apply the same rationale to fossil plants?Fragmentation of plants prior to fossilization has, however, not only left the palaeobotanist with morphological problems but has presented him with many taxonomic ones as well. Some entire plants have been reconstructed by linking a series of organically connected organs, but these are rare. Usually, fragmentation has led to difficulties in plant reconstruction as well as the determination of taxonomic relationships between dispersed organs. The binomial system of nomenclature, as used for dispersed organs, is therefore useful for convenient taxonomy, even though it has naturally produced a multiplicity of generic names for each plant. Many groupings of organs are merely reflecting similar morphologies and not necessarily any biological affinities. Genera can be given artificial parameters as Harris did for the Mesozoic conifers (1969); so we must be careful not to include such genera in any classification purporting to be natural. LycophytesAlthough there are about nine commonly accepted families of Carboniferous lycophytes, the criteria used for establishing them are often unclear and rather inconsistent. Growth habit, vegetative morphology and reproductive morphology are sometimes used alone and sometimes in conjunction. Meyen (1971) has discussed the problems of grouping fossil genera into families using examples of Gondwana and Angara phyllothecas to develop his...

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A Pennsylvanian arborescent lycopod cone, Lepidostrobus schopfii, has microspores that have been found to have intracellular features that are interpreted as nuclei and mitotic chromosomes. The cellularized gametophytes conform to the early stages of growth that occur in modern Selaginella microgametophytes. Since the megagametophyte of L. schopfii is similar in development to extant species of Isoetes, the fossil now is known to have portions of its life cycle in common with both Selaginella and Isoetes.

Middle Eocene seagrass compressions occur in the Avon Park Limestone Formation near Gulf Hammock onFlorida's west coast. One group of specimens resembles two seagrass species of the hydrocharitaceans, Thalassia and Enhalus, that are living today in tropical and subtropical shallow marine environments. The Eocene plant has a dimorphic rhizome system consisting of a creeping, monopodial, plagiotropic rhizome with small roots and orthotropic laterals (short shoots) that occur in pairs every three to five nodes. Laterals bifurcate and produce glabrous eligulate leaves in an alternate and distichous arrangement. Foliage leaves have fibrous basal sheaths, blades with parallel venation, perpendicular and oblique cross veins, prominent midrib, and smooth, entire margins. Throughout the plant are numerous brown-coloured tanniferous dots and deposits of small calcium oxalate crystals. Based on features of these non-reproductive structures, the Florida Eocene seagrass is recognized as a new genus and species Thalassites parkavonensis in the Hydrocharitaceae.

MENTE, R. F. & BRACK‐HANES, S. D., 1992. A new pinaceous seed‐cone from the Miocene of Idaho. Conifers are especially scarce in the Lower Miocene Carmen Formation in east‐central Idaho. Only two now monotypic genera, Sequoia and Glyptostrobus, are represented. Another conifer is described from the sediment based on a medium‐sized, mature, two‐year seed‐cone cast/ compression/impression with scales distinguished by abaxial apophyses without umbos. This new seed‐cone, Pityostrobus jonhalus sp. nov. Mente & Brack‐Hanes, most closely resembles Picea and Pinus (Haploxylon) of extant conifers and Pityostrobus argonnensis (Fliche) Creber of extinct conifers. Summary The new seed cone supports earlier evidence of Tertiary Pityostrobus in the western United States (Crabtree, 1987) and extends the geological range for Pityostrobus into the Miocene. By far, though, the most significant contribution of this new case/compression/impression cone is to open up possibilities for reconsidering or even reincorporating into the present literature, a considerable record of pinaceous seed cones, largely neglected because of their preservation type. Although anatomical details have been used recently as a basis for assigning fossil pinaceous cones to existing Pityostrobus species, and those features are mostly unknown for compressions, many other features can be used that are employed for extant conifer systematics, i.e. cone morphology (viz. Alvin, 1988). Consequently, comparisons of cone features regardless of preservation type, establish new potential for insight into pinaceous ancestry and the Pityostrobus complex.

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Structurally preserved arborescent lycopsid fructifications are described from Pennsylvanian age strata in eastern Kentucky and southern Illinois. Achlamydocarpon varius comb. nov. is the name proposed for these cones and previously reported isolated megasporophylls described as Lepidostrobophyllum varius. The specimens range up to 3.5 cm long and represent cone apices. Megasporophylls are spirally arranged and attached to the cone axis at an acute angle. Megasporangia are large with a wall two cell layers thick. Each sporangium contains one large, presumably functional megaspore, and three smaller, abortive megaspores. Functional and abortive spores possess a prominent apical tuft (massa) that covers up to one‐third of the proximal surface of the spore. Sporoderm ultrastructure is detailed together with a comparison of morphologically similar sporae dispersae megaspores. The possible function of the megaspore massa is discussed as it relates to the reproductive biology of the cone.