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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.
Higher up it became elliptical in cross-section, corresponding to the two rows of fertile branching units. Within the branches of these units, the strand was more-or-less rectangular. The conducting elements of the xylem, the tracheids , were of the so-called 'P-type' in which the walls were strengthened by ladder-like (scalariform) bars with ...
The family contains two genera, Psilotum and Tmesipteris. The first genus, Psilotum, consists of small shrubby plants of the dry tropics commonly known as "whisk ferns". The other genus, Tmesipteris, is an epiphyte found in Australia, New Zealand, and New Caledonia
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 ...
Cross-section of a flax plant stem: 1. Pith 2. Protoxylem 3. Xylem I 4. Phloem I 5. Sclerenchyma 6. Cortex 7. Epidermis. In botany, a cortex is an outer layer of a stem or root in a vascular plant, lying below the epidermis but outside of the vascular bundles. [1]
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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.