It is now known that some supposedly Silurian plants, such as those at Baragwanath, Vic., Australia, are actually from the Early Devonian. The Late Silurian record of Cooksonia fossils of the Czech Republic seems to be the earliest unquestionable evidence of vascular plants. Information on spores provided by palynologists would help determine the antecedents of the Devonian plants.
There was a remarkable initiation of diverse types of vascular plants during the Devonian, and a varied flora was established early in the period. Evidence of algae is common; bryophytes first appear, and charophytes are locally common. Freshwater algae and fungi are known in the Rhynie Chert of Scotland. The first known forests are of late Middle Devonian age.
The Psylotophytopsida is the most primitive group of the pteridophytes (ferns and other seedless vascular plants); this group did not survive the Late Devonian. Cooksonia, Rhynia, and others possessing a naked stem with terminal sporangia (spore cases) belong here. In other members, sporangia were borne laterally but no true leaves were developed, and the branching was often of a primitive dichotomous type. Psylotophytopsids form a basic stock from which other groups apparently evolved. Asteroxylon, which occurs with Rhynia, and other Rhynie plants in the Lower Old Red Sandstone Rhynie Chert of Scotland form a link with the lycopsids by having lateral sporangia and a dense leafy stem. Psylotophytopsids soon gave rise to treelike forms and later to the important lepidodendrids of the Carboniferous flora. Another apparent derivative, the sphenopsids, which has jointed branches, is represented by Hyenia and Pseudobornia. Pteropsids also appeared in the Devonian. Primitive gymnosperms are known, and trunks of Archaeopteris up to 1.8 metres (6 feet) in diameter are present in Upper Devonian deposits of the eastern United States and the Donets Basin of Russia and Ukraine. These trunks apparently were carried by water to their current positions.
The rich record of land plants may be related to the fact that the Old Red Sandstone represents the first widespread record of continental conditions. However, the primitive nature of the stocks seen and the absence of a long earlier record, even of detrital fragments of vascular plants, suggest that the colonization and exploitation of land environments were real Devonian events. Fortuitous finds, such as the silicified flora of the Rhynie Chert and the pyritized tissue from the Upper Devonian of New York, have enabled the intimate anatomy of many of these plants to be elucidated in detail equivalent to that of modern forms.
There was a remarkable initiation of diverse types of vascular plants during the Devonian, and a varied flora was established early in the period. Evidence of algae is common; bryophytes first appear, and charophytes are locally common. Freshwater algae and fungi are known in the Rhynie Chert of Scotland. The first known forests are of late Middle Devonian age.
The Psylotophytopsida is the most primitive group of the pteridophytes (ferns and other seedless vascular plants); this group did not survive the Late Devonian. Cooksonia, Rhynia, and others possessing a naked stem with terminal sporangia (spore cases) belong here. In other members, sporangia were borne laterally but no true leaves were developed, and the branching was often of a primitive dichotomous type. Psylotophytopsids form a basic stock from which other groups apparently evolved. Asteroxylon, which occurs with Rhynia, and other Rhynie plants in the Lower Old Red Sandstone Rhynie Chert of Scotland form a link with the lycopsids by having lateral sporangia and a dense leafy stem. Psylotophytopsids soon gave rise to treelike forms and later to the important lepidodendrids of the Carboniferous flora. Another apparent derivative, the sphenopsids, which has jointed branches, is represented by Hyenia and Pseudobornia. Pteropsids also appeared in the Devonian. Primitive gymnosperms are known, and trunks of Archaeopteris up to 1.8 metres (6 feet) in diameter are present in Upper Devonian deposits of the eastern United States and the Donets Basin of Russia and Ukraine. These trunks apparently were carried by water to their current positions.
The rich record of land plants may be related to the fact that the Old Red Sandstone represents the first widespread record of continental conditions. However, the primitive nature of the stocks seen and the absence of a long earlier record, even of detrital fragments of vascular plants, suggest that the colonization and exploitation of land environments were real Devonian events. Fortuitous finds, such as the silicified flora of the Rhynie Chert and the pyritized tissue from the Upper Devonian of New York, have enabled the intimate anatomy of many of these plants to be elucidated in detail equivalent to that of modern forms.
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