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Frond dimorphism refers to a difference in ferns between the fertile and sterile fronds. Since ferns, unlike flowering plants, bear spores on the leaf blade itself, this may affect the form of the frond itself. In some species of ferns, there is virtually no difference between the fertile and sterile fronds, such as in the genus Dryopteris , other than the mere presence of the sori, or fruit-dots, on the back of the fronds. Some other species, such as Polystichum acrostichoides (Christmas fern), or some ferns of the genus Osmunda , feature dimorphism on a portion of the frond only. Others, such as some species of Blechnum and Woodwardia , have fertile fronds that are markedly taller than the sterile. Still others, such as Osmunda cinnamomea (Cinnamon fern), or plants of the family Onocleaceae, have fertile fronds that are completely different from the sterile.
Only members of the Onocleaceae and Blechnaceae exhibit a propensity towards dimorphy, while no member of the Athyriaceae is strongly dimorphic, and only some representatives of the Thelypteridaceae have evolved the condition, suggesting a possible close relationship between Onocleaceae and Blechnaceae. [1]
Its importance has been disputed - Copeland for example, considered it taxonomically important, [2] whereas Tryon and Tryon [3] and Kramer [4] all stated that the importance can only be judged in relation to other characteristics. [1]
A fern is a member of a group of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses and other bryophytes by being vascular, i.e., having specialized tissues that conduct water and nutrients and in having life cycles in which the branched sporophyte is the dominant phase. Ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns. They produce coiled fiddleheads that uncoil and expand into fronds. The group includes about 10,560 known extant species. Ferns are defined here in the broad sense, being all of the Polypodiopsida, comprising both the leptosporangiate (Polypodiidae) and eusporangiate ferns, the latter group including horsetails or scouring rushes, whisk ferns, marattioid ferns, and ophioglossoid ferns.
The Osmundaceae is a family of four to six extant genera and 18–25 known species. It is the only fern family of the order Osmundales an order in the class Polypodiopsida (ferns) or in some classifications the only order in the class Osmundopsida. This is an ancient and fairly isolated group that is often known as the "flowering ferns" because of the striking aspect of the ripe sporangia in Claytosmunda, Osmunda, Osmundastrum, and Plensium. In these genera the sporangia are borne naked on non-laminar pinnules, while Todea and Leptopteris bear sporangia naked on laminar pinnules. Ferns in this family are larger than most other ferns.
A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the large leaves of cycads, as well as palms (Arecaceae) and various other flowering plants, such as mimosa or sumac. "Frond" is commonly used to identify a large, compound leaf, but if the term is used botanically to refer to the leaves of ferns and algae it may be applied to smaller and undivided leaves.
Osmunda is a genus of primarily temperate-zone ferns of family Osmundaceae. Five to ten species have been listed for this genus.
Platycerium is a genus of about 18 fern species in the polypod family, Polypodiaceae. Ferns in this genus are widely known as staghorn or elkhorn ferns due to their uniquely shaped fronds. This genus is epiphytic and is native to tropical and temperate areas of South America, Africa, Southeast Asia, Australia, and New Guinea.
Onoclea is a genus of plants in the family Onocleaceae, native to moist habitats in eastern Asia and eastern North America. They are deciduous ferns with sterile fronds arising from creeping rhizomes in spring, dying down at first frost. Fertile fronds appear in late summer. Depending on the authority, the genus contains one to five species.
Blechnaceae is a family of ferns in the order Polypodiales, with a cosmopolitan distribution. Its status as a family and the number of genera included have both varied considerably. In the Pteridophyte Phylogeny Group classification of 2016, the family has 24 genera, and excludes genera placed in the separate family Onocleaceae. The family is divided into three subfamilies, including Blechnoideae s.s. Alternatively, the entire family may be treated as the subfamily Blechnoideae s.l. of a very broadly defined family Aspleniaceae, and include genera others place in Onocleaceae.
Claytosmunda is a genus of fern. It has only one species, Claytosmunda claytoniana, the interrupted fern, native to Eastern Asia, Eastern United States, and Eastern Canada.
Osmunda regalis, or royal fern, is a species of deciduous fern, native to Europe, Africa and Asia, growing in woodland bogs and on the banks of streams. The species is sometimes known as flowering fern due to the appearance of its fertile fronds.
Osmundastrum is genus of leptosporangiate ferns in the family Osmundaceae with one accepted species, Osmundastrum cinnamomeum, the cinnamon fern. It is native to the Americas and eastern Asia, growing in swamps, bogs and moist woodlands.
Osmunda japonica, also called Asian royal fern, is a fern in the genus Osmunda native to east Asia, including Japan, China, Korea, Taiwan, and the far east of Russia on Sakhalin. It is called gobi (고비) in Korean and zenmai in Japanese.
Lorinseria is a genus of fern in the subfamily Woodwardioideae of the family Blechnaceae. Its only species is Lorinseria areolata, the netted chain fern, native to eastern North America. The monotypic genus Lorinseria has been separated from Woodwardia in the Pteridophyte Phylogeny Group classification of 2016, on the basis of its anastamosing veins and lobed frond form, as well as its more marked frond dimorphism. However, the genus name Lorinseria appears to be a later homonym of LorinseraOpiz, and will need to be replaced or conserved.
Blechnum, known as hard fern, is a genus of ferns in the family Blechnaceae, subfamily Blechnoideae, according to the Pteridophyte Phylogeny Group classification of 2016. Two very different circumscriptions of the genus are used by different authors. In the PPG I system, based on Gasper et al. (2016), Blechnum is one of 18 genera in the subfamily Blechnoideae, and has about 30 species. Other sources use a very broadly defined Blechnum s.l., including accepting only two other genera in the subfamily. The genus then has about 250 species. In the PPG I circumscription, the genus is mostly neotropical, with a few southern African species.
Onocleaceae is a small family of terrestrial ferns in the order Polypodiales. It is placed in the suborder Aspleniineae in the Pteridophyte Phylogeny Group classification of 2016. Alternatively, the family, along with Blechnaceae, may be placed in a very broadly defined family Aspleniaceae as the subfamily Blechnoideae. The family may contain from one to four genera, consisting of five species largely in north temperate climes. The four genera, Matteuccia, Onoclea, Onocleopsis and Pentarhizidium, may be included under the single genus Onoclea.
Struthiopteris spicant, syn. Blechnum spicant, is a species of fern in the family Blechnaceae, known by the common names hard-fern or deer fern. It is native to Europe, western Asia, northern Africa, and western North America. Like some other species in the family Blechnaceae, it has two types of leaves. The sterile leaves have flat, wavy-margined leaflets 5 to 8 millimeters wide, while the fertile leaves have much narrower leaflets, each with two thick rows of sori on the underside.
Botrychium lunaria is a species of fern in the family Ophioglossaceae known by the common name moonwort or common moonwort. It is the most widely distributed moonwort, growing throughout the Northern Hemisphere across Eurasia and from Alaska to Greenland, as well as temperate parts of the Southern Hemisphere.
Parablechnum wattsii, synonym Blechnum wattsii, is a common terrestrial fern growing in rainforest and open forest. It is often seen near creeks in much of south eastern Australia, including Victoria, Tasmania, South Australia, New South Wales and Queensland. The specific epithet wattsii honours William Walter Watts (1856-1920). Watts was considered an authority on mosses and ferns and has more than 30 species named for him. Common names by which the species may be called are hard water fern - from its stiff leathery fronds, leech fern - as forest workers often encounter leaches while working in clusters of these ferns, hard hill fern - from the fern's habit and habitat, and red cabbage fern - from the bronze-pink colour of the young fronds resembling cooked red cabbage.
Lomaria nuda, commonly known as the fishbone waterfern, is a fern that grows up to a metre tall, and is abundant in rainforest and eucalyptus forests in eastern Australia. The species is placed in the genus Lomaria in the Pteridophyte Phylogeny Group classification of 2016, but is often retained in genus Blechnum as Blechnum nudum.
Sceptridium dissectum is a common fern in the family Ophioglossaceae, occurring in eastern North America. Like other plants in this group, it normally only sends up one frond per year. It has long been the subject of confusion because the frond presents in one of two forms, either the normal form that resembles other plants in the genus, or the skeletonized form.
Osmunda spectabilis, known as American royal fern, is a species of fern native to a large area of the New World, from Canada to Argentina.