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 and palms (Arecaceae). "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.
Asplenium platyneuron, commonly known as ebony spleenwort or brownstem spleenwort, is a fern native to North America east of the Rocky Mountains and to South Africa. It takes its common name from its dark, reddish-brown, glossy stipe and rachis, which bear a once-divided, pinnate leaf. The fertile fronds, which die off in the winter, are darker green and stand upright, while the sterile fronds are evergreen and lie flat on the ground. An auricle at the base of each pinna points towards the tip of the frond. The dimorphic fronds and alternate, rather than opposite, pinnae distinguish it from the similar black-stemmed spleenwort.
Adiantum capillus-veneris, the Southern maidenhair fern, black maidenhair fern, maidenhair fern, and venus hair fern, is a species of ferns in the genus Adiantum and the family Pteridaceae with a subcosmopolitan worldwide distribution. It is cultivated as a popular garden fern and houseplant.
Asplenium montanum, commonly known as the mountain spleenwort, is a small fern endemic to the eastern United States. It is found primarily in the Appalachian Mountains from Vermont to Alabama, with a few isolated populations in the Ozarks and in the Ohio Valley. It grows in small crevices in sandstone cliffs with highly acid soil, where it is usually the only vascular plant occupying that ecological niche. It can be recognized by its tufts of dark blue-green, highly divided leaves. The species was first described in 1810 by the botanist Carl Ludwig Willdenow. No subspecies have been described, although a discolored and highly dissected form was reported from the Shawangunk Mountains in 1974. Asplenium montanum is a diploid member of the "Appalachian Asplenium complex," a group of spleenwort species and hybrids which have formed by reticulate evolution. Members of the complex descended from A. montanum are among the few other vascular plants that can tolerate its typical habitat.
Asplenium pinnatifidum, commonly known as the lobed spleenwort or pinnatifid spleenwort, is a small fern found principally in the Appalachian Mountains and the Shawnee Hills, growing in rock crevices in moderately acid to subacid strata. Originally identified as a variety of walking fern, it was classified as a separate species by Thomas Nuttall in 1818. It is believed to have originated by chromosome doubling in a hybrid between walking fern and mountain spleenwort, producing a fertile tetraploid, a phenomenon known as alloploidy; however, the hypothesized parental hybrid has never been located. It is intermediate in morphology between the parent species: while its leaf blades are long and tapering like that of walking fern, the influence of mountain spleenwort means that the blades are lobed, rather than whole. A. pinnatifidum can itself form sterile hybrids with several other spleenworts.
Asplenium bradleyi, commonly known as Bradley's spleenwort or cliff spleenwort, is a rare epipetric fern of east-central North America. Named after Professor Frank Howe Bradley, who first collected it in Tennessee, it may be found infrequently throughout much of the Appalachian Mountains, the Ozarks, and the Ouachita Mountains, growing in small crevices on exposed sandstone cliffs. The species originated as a hybrid between mountain spleenwort and ebony spleenwort ; A. bradleyi originated when that sterile diploid hybrid underwent chromosome doubling to become a fertile tetraploid, a phenomenon known as allopolyploidy. Studies indicate that the present population of Bradley's spleenwort arose from several independent doublings of sterile diploid hybrids. A. bradleyi can also form sterile hybrids with several other spleenworts.
Adiantum alarconianum is a South American maidenhair fern. First scientifically collected in the early 1800s in Ecuador, it is found in neighboring parts of Peru as well. Its iridescent stem scales help to differentiate it from other related ferns.
Asplenium × ebenoides is a hybrid fern native to eastern North America, part of the "Appalachian Asplenium complex" of related hybrids. The sterile offspring of the walking fern (A. rhizophyllum) and the ebony spleenwort (A. platyneuron), A. × ebenoides is intermediate in morphology between its two parents, combining the long, narrow blade of A. rhizophyllum with a dark stem and lobes or pinnae similar to those of A. platyneuron. While A. × ebenoides is generally sterile, fertile specimens with double the number of chromosomes are known from Havana Glen, Alabama. These fertile allotetraploids were reclassified as a separate species named A. tutwilerae in 2007, retaining the name A. × ebenoides for the sterile diploids only.
Asplenium × wherryi, known as Wherry's spleenwort, is a rare hybrid fern of the Appalachian Mountains. The sterile triploid offspring of mountain spleenwort (A. montanum) and Bradley's spleenwort (A. bradleyi), it is known from a few sites where those species grow together. First collected by Edgar T. Wherry in 1935, it was largely ignored until a new colony was found in 1961, and the species was named in his honor.
Asplenium × gravesii, commonly known as Graves' spleenwort, is a rare, sterile, hybrid fern, named for Edward Willis Graves (1882–1936). It is formed by the crossing of Bradley's spleenwort (A. bradleyi) with lobed spleenwort (A. pinnatifidum). It is only found where its parent species are both present; in practice, this proves to be a few scattered sites in the Appalachian Mountains, Shawnee Hills, and Ozarks, reaching perhaps its greatest local abundance around Natural Bridge State Resort Park. Like its parents, it prefers to grow in acid soil in the crevices of sandstone cliffs.
Asterotheca is a genus of seedless, spore-bearing, vascularized ferns dating from the Carboniferous of the Paleozoic to the Triassic of the Mesozoic.
Asplenium × boydstoniae, commonly known as Boydston's spleenwort, is a rare, sterile, hybrid fern. It is formed by the crossing of Tutwiler's spleenwort (A. tutwilerae) with ebony spleenwort (A. platyneuron). The hybrid was produced in culture in 1954. It was not discovered in the wild until 1971, when it was found by Kerry S. Walter at Havana Glen, Alabama, the only known wild site for Tutwiler's spleenwort. Walter named it for Kathryn E. Boydston, an expert in fern culture. Except for the tip of its leaf blade, it largely resembles its ebony spleenwort parent.
Myriopteris lanosa, the hairy lip fern, is a moderately-sized fern of the eastern United States, a member of the family Pteridaceae. Its leaves and stem are sparsely covered in hairs, but lack scales, hence its common name. One of the cheilanthoid ferns, it was usually classified in the genus Cheilanthes until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows in shallow, dry, soil, often in rocky habitats.
Myriopteris alabamensis, the Alabama lip fern, is a moderately-sized fern of the United States and Mexico, a member of the family Pteridaceae. Unlike many members of its genus, its leaves have a few hairs on upper and lower surfaces, or lack them entirely. One of the cheilanthoid ferns, it was usually classified in the genus Cheilanthes until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows in shade on limestone outcrops.
Myriopteris aemula, the Texas lip fern or rival lip fern, is a moderately-sized fern of Texas and Mexico, a member of the family Pteridaceae. Unlike many members of its genus, its leaves have a few hairs on upper and lower surfaces, or lack them entirely. One of the cheilanthoid ferns, it was usually classified in the genus Cheilanthes until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows on limestone rock.
Myriopteris allosuroides is a moderately-sized fern of Mexico, a member of the family Pteridaceae. Unlike many members of its genus, its rachides are grooved on the upper surface and largely free of hairs or scales. One of the cheilanthoid ferns, it was usually classified in the genera Cheilanthes or Pellaea until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows on dry, rocky slopes over acidic, particularly basaltic, rock.
