Structure of Tracheids in Three Species of Lycopodium

The development and/or modification of special acid etching and macerating techniques permits pyritized fossils of Leclercqia complexa to be separated into their carbonaceous wall remains and pyrite lumen—pit casts. These carbonized and pyritic portions can then be studied separately by both light and SEM microscopy and information from both modes compared with that obtainable from carbonaceous compression fossils of L. complexa. This combination of techniques, preservation modes and methods of analysis, allows a synthesis of information obtainable from each, as well as providing a check on errors of interpretation due to preservation mode and method of observation. The developmental sequence of the secondary wall thickenings of the protoxylem elements is shown to be annular to connected annular and spiral, with both exarch and mesarch maturation. The metaxylem shows a transition through reticulate to multiseriate round, oval, and elongate bordered‐pitted tracheids. Different wall facets of separated pyrite tracheid casts can be examined by the SEM and variations in wall structure and pitting characterized. Cells of the outer cortex are 6 to 10 times longer than wide, have thickened vertical walls and end walls that vary from nearly horizontal to angles of overlap of 50 degrees.

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confidence: 89%

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confidence: 99%

“…Many early authors have reported helical elements in living Lycopodium (see Wilder, 1970, for a review). Wilder (1970) observed ". Wilder (1970) observed ".…”

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confidence: 99%

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confidence: 99%

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confidence: 99%

See 3 more Smart Citations

Leclercqia Complexa (Lycopsida, Middle Devonian): Its Anatomy, and the Interpretation of Pyrite Petrifactions

Grierson

1976

A Comparative Study of the Foliar Anatomy of Lycopodium Species

Chu

1974

A comparative study of the leaves of 31 species of Lycopodium was made. The pattern of tracheids varies with the species. Usually they exhibit annular, helical, reticulate, modified or transition forms; none of the species have advanced phylogenetically beyond the scalariform tracheid stage. Mucilage canals have been found in four species. Tracheids are enclosed by a few to several layers of oblique ended, elongated parenchyma cells in most species, but an endodermis is absent. Vascular bundles are encircled by fiber cells in three species. The mesophyll of most species consists of identically shaped cells, although palisade‐like tissue has been observed in a few species. The epidermal cells vary from elongated to isodiametric and have either undulated or smooth anticlinal walls, which are deeply pitted in some species. The outer epidermal walls are usually thick and heavily cutinized. Stomates are distributed on both surfaces in 18 species, on the abaxial surface in 11 species, and on the adaxial side in only two species. Most stomates are practically isodiametric in surface view, broader than epidermal cells, usually parallel to the vein, and at the same level as the adjacent epidermal cell. A typical guard cell has a prominent outer ledge and a less developed inner ledge of cutin in most species. Six groupings are suggested, based on similarity of leaf structure and the known chromosome numbers.

Barinophyton Citrulliforme (Barinophytales Incertae Sedis, Barinophytaceae) From the Upper Devonian of Pennsylvania

Brauer

1980

Barinophyton citrulliforme is definitely proven to be a tracheophyte. The vascular cylinder of the main axis is an exarch protostele composed of tracheids having a continuous secondary wall folded into protrusions into the cell lumen. These protrusions delineate the position of annular thickenings which were deposited earlier than the continuous secondary wall. Between successive protrusions, the later-deposited secondary wall is interrupted by minute pitlike structures. It is suggested that the secondary walls of the tracheids were laid down in a twophase depositional sequence. The fertile system of B. citrulliforme consists of a main axis bearing spirally arranged strobili. The strobilus consists of an axis that bears two alternate rows of sporangiferous appendages. The sporangiferous appendages are borne laterally along the strobilar axis and recurve abaxially around the axis. The sporangia are attached along the inside curve of the appendages, one sporangium per appendage, each containing both microspores and megaspores. This species thus exhibits sporangial heterospory which is considered to be an adaptation to an aquatic habit and the sporangia are considered to be functional analogs of the sporocarps of Marsilea, The interpretation of the strobilus is morphologically identical to Ananiev's interpretation of the strobilus of Pectinophyton bipectinatum ; consequently P. hipectinaturn is here transferred to Barinophyton as B. robustius comb. nov.