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 Add this item to the list  802281 Original description
Description type:Original description 
Description:The reproductive units occur singly in largely degraded land plant axes, probably of Horneophyton lignieri (Kidston et Lang) Barghoorn et Darrah; six specimens have been discovered to date. Vegetative mycelia co-occurring with the reproductive units have not been found. The units are globose to somewhat ovoid (subglobose) in shape and up to 40(–50) μm in diameter (inclusive investment). All are composed of a central cavity surrounded by a prominent investment up to 10 µm thick. The investment is constructed of two different elements, with the outer, prominent element composed of hyphae, and the inner element non-hyphal. The central cavity has a diameter of up to 35 µm and all specimens lack contents. The outer, hyphal investment element is up to 9.5 µm thick, and consists of a system of irregularly swollen to catenulate, interlaced hyphae, which are relatively thin-walled; septa are present. Hyphae are between 1.5 and 2.1 µm wide, while hyphal swellings are variable in size and shape (i.e. spheroidal, short-elliptical, elongate-clavate, or sometimes sub-cylindrical), and up to 6(–8) µm long and 3–6 µm wide. The swellings generally increase in size towards the periphery of the hyphal investment. Tubular or irregularly swollen hyphae up to 2.5 µm wide, extending around the circumference of the reproductive unit, may be present in the periphery. The inner, non-hyphal investment element is recognizable in most of the specimens as a distinctive, very regular opaque line (~0.3–0.65 µm thick) extending along the inner surface of the hyphal investment; irregularities in the form of local wrinkling or distortion may occur, but seem to be rare. One of the specimens, however, possesses a considerably more massive non-hyphal inner investment element that is up to 3 μm thick. Several specimens suggest that the outer, hyphal investment element was somehow involved in the size increase of the inner element. In some of the specimens, small opaque granules are integrated into the non-hyphal investment element. A short, papilla-like protrusion of the non-hyphal investment element is visible in one specimen, whereas in two other reproductive units opaque plaques occur in the position where a parental hypha or filament probably was attached. Associated with one of the reproductive units is a smaller structure that appears to be constructed of at least two bulbous components. We are uncertain whether this structure was organically connected with the reproductive unit. 
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