Psilophytales (psilophytes) Primitive pteridophytes, which were the earliest vascular plants, from the Silurian and the Devonian. They had slender, tapering, leafless or scale-bearing stems up to 50 cm high, often with cone-shaped sporangia (see SPORE) at the top. Some authorities placed the fossil groups with the present-day psilophytes (Psilotum, Tmesipteris) in the class Psilopsida, comprising the orders Psilotales (living forms) and Psilophytales (fossil forms). In more recent classifications the members of the Psilophytales have been placed into three separate groups, usually ranked as subdivisions: Rhyniophytina (e.g. Cooksonia and Rhynia); Trimerophytina (e.g. Psilophyton and Trimerophyton); and Zosterophyllophytina (e.g. Zosterophyllum). The living forms are contained in a fourth subdivision, the Psilophytina.
Psilophytales Primitive pteridophytes, which were the earliest vascular plants, from the Silurian and Devonian. They had slender, tapering, leafless, or scale-bearing stems up to 50 cm high, often with cone-shaped sporangia at the top. Recent classifications also include the living psilophytes in this group. The modern psilophytes (Psilopsida) comprise 4 or 5 plant species of the tropics and subtropics, of which Psilotum (whisk fern) is the best known.
More From encyclopedia.com
Silicate , silicate silicates The most important and abundant group of rock-forming minerals, which can be classified according to the structural arrangement of… Radial Symmetry , Skip to main content radial symmetry radial symmetry The arrangement of parts in an organ or organism such that cutting through the centre of the str… Hygroscopic Nucleus , hygroscopic nucleus Microscopic particle (e.g. of sulphur dioxide, salt, dust, or smoke) in the free air, on which water vapour may condense to form… Dicotyledoneae , Dicotyledoneae One of the two classes of flowering plants (see Anthophyta), distinguished by having two seed leaves (cotyledons) within the seed. The… Hemicryptophyte , hemicryptophyte One of Raunkiaer's life-form categories, being a plant whose perennating buds are at ground level, the aerial shoots dying down at th… Alum , alum (ăl´əm), any one of a series of isomorphous double salts that are hydrated sulfates of a univalent cation (e.g., potassium, sodium, ammonium, ce…
About this article
All Sources -
Updated About encyclopedia.com content Print Topic