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A central strand of xylem occupied up to a third of the diameter of the stem. In the lower parts of main stems it was circular, enlarging before it divided prior to dichotomous branching. Higher up it became elliptical in cross-section, corresponding to the two rows of fertile branching units.
Psilotum is a genus of fern-like vascular plants.It is one of two genera in the family Psilotaceae commonly known as whisk ferns, the other being Tmesipteris.Plants in these two genera were once thought to be descended from the earliest surviving vascular plants, but more recent phylogenies place them as basal ferns, as a sister group to Ophioglossales.
Psilotum nudum, the whisk fern, [3] is a fernlike plant. Like the other species in the order Psilotales, it lacks roots. [4]Its name, Psilotum nudum, means "bare naked" in Latin, because it lacks (or seems to lack) most of the organs of typical vascular plants, as a result of evolutionary reduction.
Psilotum has been interpreted as producing sporangia (fused in a synangium) on the terminus of a stem. Equisetum always produce strobili, but the structures bearing sporangia (sporangiophores) have been interpreted as modified stems. The sporangia, despite being recurved are interpreted as terminal.
In plant anatomy and evolution a microphyll (or lycophyll) is a type of plant leaf with one single, unbranched leaf vein. [1] Plants with microphyll leaves occur early in the fossil record, and few such plants exist today. In the classical concept of a microphyll, the leaf vein emerges from the protostele without leaving a leaf gap. Leaf gaps ...
Tmesipteris obliqua, more commonly known as the long fork-fern or common fork-fern, is a weeping, epiphytic fern ally with narrow unbranched leafy stems. [1] T. obliqua is a member of the genus Tmesipteris, commonly known as hanging fork-ferns. Tmesipteris is one of two genera in the order Psilotales, the other genus being Psilotum. [2]
F bicollateral open Cross section of celery stalk, showing vascular bundles, which includes both phloem and xylem Detail of vascular bundle: closed, collateral vascular bundles of the stem axis of Zea mays Vascular bundle in the leaf of Metasequoia glyptostroboides The vascular bundle of pine leaf showing xylem and phloem
Pedicel – the stem or stalk that holds a single flower in an inflorescence. Peduncle – the part of a stem that bears the entire inflorescence, normally having no leaves, or the leaves having been reduced to bracts. When the flower is solitary, it is the stem or stalk holding the flower. Peduncular – referring to or having a peduncle.