Australia, Africa, South America, Antarctica
The Glossopteridales are an order of extinct group of plants the seed ferns. They were widespread in the Permian on the southern continent Gondwana, particularly the eponymous genus Glossopteris, which is why these plants is called Glossopteris flora. Characteristic are the tongue-shaped leaves, of which the name derives (Greek glossis = tongue, pteris = Fern ).
From Glossopteris is believed that they grew tree -shaped. The wood of Glossopteris is pyknoxyl ( dense wood with little parenchyma ) with distinct growth rings. It is sometimes placed in the Morphogattung Araucarioxylon. Here is the cup of the tracheids are on the radial walls in rows, some pits are hexagonal. The Xylemstrahlen are uniseriate. The strain at Glossopteris skaarensis has a Eustele whose tracheids have bordered pits round.
The underground organs ranged not very deep and are placed in the genus Vertebraria. In the center is a exarches primary xylem, which is surrounded by four to seven rays secondary wood, which are separated by voids. The secondary xylem has growth rings. To the secondary timber is a thin, corked periderm. The primary xylem is formed by ring - tracheids of the secondary Tüpfeltracheiden.
The leaves were changing constantly, or arranged in tight bolts on the axles. There are strong indications that the leaves were seated at long and short shoots, similar to the ginkgo. Glossopteris threw in the fall from the leaves. Most leaves are found individually.
Glossopteris is by far the most traditional genre. The leaves are lanceolate and have a distinct midrib, and a Netznervatur. More than 200 species have been described. One of the most common types is Glossopteris browniana whose leaves are about 30 inches long and have a round tip. At Glossopteris fibrosa the epidermis was examined: stomata are restricted to the lower leaf surface and surrounded by four to eight accessory cells. Some species bear on the bottom hair.
The leaf anatomy could be studied only in a few species. Glossopteris schopfii has four to five vascular bundles in the midrib. The vascular bundles are surrounded by a bundle sheath of thick-walled fiber cells. The density of stomata, just sitting on the bottom here is 40 per mm ². The midrib of Glossopteris skaarensis consists of a single, wide vascular bundles with wire tracheids, which is surrounded by a thin-walled bundle sheath. In Triassic forms and petioles are known.
Gangamopteris is a genus which occurred mainly in the Lower Permian, their leaves do not have a clear midrib. Other common genera are Belemnopteris sheet and Rhabdotaenia are rarer Rubidgea, Palaeovittaria and Euryphyllum.
The reproductive organs - ovules and pollen sacs - are on deciduous leaves or of modified leaves. Male and female organs are always on separate sheets.
Ovule -bearing organs
The female organs consist of a dorsiventral structure on which the seeds are produced. This structure was named differently: capitulum, Megasporophyll, cupula, Fertiliger. Some of these bodies may have formed cones.
The morphology of the seed-bearing structures is very diverse compared to the vegetative structures. Some examples are:
- Scutum is a Morphogattung the ovules -carrying structure is plate -like. The central part, where the ovules are sitting, is surrounded by a wing margin. Ottokaria has a slender stem with a fan-like head, on the adaxial ( toward the axis ) seated seeds. Whether the stem springs from the midrib of the leaf or the leaf axil, is not assured. Austroglossa walkomii carry up to 20 seated seeds at each stalked head, sitting on the petioles of Glossopteris conspicua.
- Lidgeottia is a composite structure, sit at the four to eight seed-bearing structures ( Megasporophylle ) on a leaf. Each Megasporophyll is disc-shaped and has a diameter of approximately seven millimeters. The edge is lobed to toothed. The seeds from Samaropsis type have a diameter of two millimeters and are winged.
- In Rusangea from South Africa protrude from each leaf two stems, each carrying only a seed. Rusangea elegans has around 2.8 centimeters long leaves with wingless, oval seeds of 3.5 mm size.
- Denkania has six seed-bearing cupulae, each standing on a long stem on a Glossopteris leaf. Each is about an inch tall and wears only one seed.
- From the Late Permian of Queensland Megasporophylle of Glossopteris are known, which are rolled up. In the cavity thus formed are located approximately 1.5 mm ovules. The cavity is filled with filaments, which may in the steering of the pollen grains have played a role.
Common seed forms are Pterygospermum and Stephanostoma.
Pollen - producing organs
Pollen -bearing organs were found much less frequently than seed-bearing. One of the most common is Glossotheca: it consists of stalks, which spring from the petiole of the leaf blade. At the end of the stalks are groups of up to 100 elongate pollen sacs.
Individual pollen sacs, which are assigned to the Glossopteridales are Arberiella, Lithangium and Polytheca whose sporangia are unilocular. The pollen grains in Arberiella have two air bags are so bisaccat. In Arberiella vulgaris they are 85 microns long. In Lithangium the pollen grains are monolet ( only have a scar ), monocolpat at Polytheca ( have a seed furrow ).
The Glossopteridales probably populated marshy terrain. This is concluded from the air-filled structures of the rhizomes.
They were adapted to a strongly seasonal climate, but they populated areas between 40 and 90 ° south latitude. Thick layers of single sheets suggest leaf fall. The annual rings in the wood indicate seasons.
The Glossopteridales were spread on whole Gondwana continent and are now found in Australia, Africa, South America and Antarctica. They were the vegetation influential clan in this area during the late Paleozoic.
The relationships of the Glossopteridales are not released. They have characteristics of several groups, however, are the seeds of ferns most similar to which they are made.
Schopf put them in the vicinity of the Gnetales and suspected in the Glossopteridales their ancestors. Cladistic studies by Doyle and Donoghue they found in the vicinity of the angiosperms.
Glossopteris was first described by Adolphe Brongniart 1828 in detail. The Glossopteridales or their representatives were initially assigned to different groups, so the cycads, seed ferns, Gnetophyta, Cordaitales and the angiosperms. It was not until the discovery of seed-bearing Megasporophyllen 1977 that belonged to known representatives, the classification made clear at the seed ferns.
The distribution of Glossopteris was one of the main arguments in the early discussion of the theory of continental drift and the existence of a southern continent ( Gondwana ).