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Asplenium × Gravesii
''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. Description ''Asplenium'' × ''gravesii'' is a small fern, whose fronds grow in loosely bundled tufts. Its stem below the leaf blade is a shiny purplish-brown, while the green, narrowly triangular blades are cut into pinnae near the base, which diminish into lobes in the upper part. The fronds are monomorphic, showing little or no difference between sterile and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Ralph Maxon
William Ralph Maxon, (February 27, 1877February 25, 1948) was an American botanist and pteridologist. He graduated from Syracuse University with a Bachelor of Philosophy, B.Ph. in biology, in 1898, and spent about one year at Columbia University doing post-graduate work on ferns with Lucien Marcus Underwood. In 1899 he accepted a position with the National Museum of Natural History, United States National Museum, which was a part of the Smithsonian Institution; he remained at the museum for his entire career. In 1899 he became an aide with the Division of Plants. He was named assistant curator in 1905, associate curator in 1914, and curator of that Division in 1937. He retired in 1946, but continued his association with the museum until his death in 1948. For the current version of this webpage, see . The later version does not indicate authorship. Alan Bain has written that, "Maxon specialized in the taxonomic study of Pteridophyta, especially those of tropical America, and was con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asplenium × Trudellii
''Asplenium'' × ''trudellii'', commonly known as Trudell's spleenwort, is a rare hybrid fern of the eastern United States, first species description, described in 1925. It is formed by the crossing of mountain spleenwort (Asplenium montanum, ''A. montanum'') with lobed spleenwort (Asplenium pinnatifidum, ''A. pinnatifidum''). Trudell's spleenwort is intermediate in form between its two parents, and is generally found near them, growing on exposed outcrops of acidic rock. While ''A. × trudellii'' is triploid and sterile, there is some evidence that it can occasionally reproduce apomixis, apogamously. Description ''Asplenium'' × ''trudellii'' is a small fern, with evergreen fronds growing in tufts. It is similar to ''A. pinnatifidum'', with a triangular leaf blade, pinnatifid (lobed) in the upper part, with a long, drawn-out tip. The fronds are monomorphic, showing little or no difference between sterile and fertile fronds. Fronds of a lar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asplenium Montanum
''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 tol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately result in four cells with only one copy of each chromosome ( haploid). Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and female will fuse to create a cell with two copies of each chromosome again, the zygote. Errors in meiosis resulting in aneuploidy (an abnormal number of chromosomes) are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number of chr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stomata
In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the stomatal opening. The term is usually used collectively to refer to the entire stomatal complex, consisting of the paired guard cells and the pore itself, which is referred to as the stomatal aperture. Air, containing oxygen, which is used in respiration, and carbon dioxide, which is used in photosynthesis, passes through stomata by gaseous diffusion. Water vapour diffuses through the stomata into the atmosphere in a process called transpiration. Stomata are present in the sporophyte generation of all land plant groups except liverworts. In vascular plants the number, size and distribution of stomata varies widely. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herb Wagner
Warren Herbert Wagner Jr. (August 29, 1920 – January 8, 2000) was an eminent American botanist who was trained at Berkeley with E.B. Copeland and lived most of his professional career in Michigan. History Wagner was instructed in the ways of plant microphotograph and embryology by Marion S. Cave. Wagner was a longtime faculty member at the University of Michigan. He was most respected among his colleagues and students for his genius in discerning and articulating the differences in form between plant species in the context of their variation with environmental factors. He developed, in the early 1960s, the first algorithm for discerning phylogenetic relationships among species based upon their respective character states observed over a set of characters. This work was honored by James Farris and Arnold Kluge in their later appellation of related algorithms as "Wagner parsimony." Wagner became a pteridologist later in life, specializing in ferns, especially the Botrychi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Susquehanna River
The Susquehanna River (; Lenape: Siskëwahane) is a major river located in the Mid-Atlantic region of the United States, overlapping between the lower Northeast and the Upland South. At long, it is the longest river on the East Coast of the United States. By watershed area, it is the 16th-largest river in the United States,Susquehanna River Trail Pennsylvania Fish and Boat Commission, accessed March 25, 2010.Susquehanna River , Green Works Radio, accessed March 25, 2010. and also the longest river in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William R
William is a male given name of Germanic origin.Hanks, Hardcastle and Hodges, ''Oxford Dictionary of First Names'', Oxford University Press, 2nd edition, , p. 276. It became very popular in the English language after the Norman conquest of England in 1066,All Things William"Meaning & Origin of the Name"/ref> and remained so throughout the Middle Ages and into the modern era. It is sometimes abbreviated "Wm." Shortened familiar versions in English include Will, Wills, Willy, Willie, Bill, and Billy. A common Irish form is Liam. Scottish diminutives include Wull, Willie or Wullie (as in Oor Wullie or the play ''Douglas''). Female forms are Willa, Willemina, Wilma and Wilhelmina. Etymology William is related to the given name ''Wilhelm'' (cf. Proto-Germanic ᚹᛁᛚᛃᚨᚺᛖᛚᛗᚨᛉ, ''*Wiljahelmaz'' > German ''Wilhelm'' and Old Norse ᚢᛁᛚᛋᛅᚼᛅᛚᛘᛅᛋ, ''Vilhjálmr''). By regular sound changes, the native, inherited English form of the name shoul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trenton, Georgia
Trenton is a city and the only incorporated municipality in Dade County, Georgia, United States—and as such, it serves as the county seat. The population was 2,195 at the 2020 census. Trenton is part of the Chattanooga, Tennessee–GA Metropolitan Statistical Area. History Founded in the 1830s, the area was originally known as Salem. In 1839 Salem was designated the seat of the newly formed Dade County. It was renamed Trenton in 1841. The present name is a transfer from Trenton, the state capital of New Jersey. Geography Trenton is located at (34.875609, −85.508644). The city is located in the northwestern part of the state along Interstate 59, which runs from southwest to northeast to the west of the city, leading northeast 20 mi (32 km) to Chattanooga, Tennessee (via I-59 to I-24), and southwest 128 mi (206 km) to Birmingham, Alabama. U.S. Route 11 and Georgia State Route 136 are the main roads through the center of the city, with U.S. 11 leading ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sand Mountain (Alabama)
Sand Mountain is a sandstone plateau in northeastern Alabama and (to a far lesser extent) northwestern Georgia (U.S. state), Georgia and southeastern Tennessee (U.S. state), Tennessee where the plateau is known as Raccoon Mountain Pumped-Storage Plant, Raccoon Mountain and Elder Mountain. It is part of the southern tip of the Appalachian Mountains, Appalachian mountain chain and it is the largest plateau in the chain. Geologically a continuation of Walden Ridge, Sand Mountain is part of the Cumberland Plateau, separated from the main portion of the plateau by the Tennessee River and Sequatchie Valley. The average elevation on Sand Mountain is around above sea level, compared to about in the surrounding area.Google Earth This elevation leads to its having the coolest climate in the state of Alabama. The largest city on Sand Mountain is Albertville, Alabama, Albertville, in Marshall County. As of the 2010 census, the population of the city was 21,160. History Prehistory through ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guard Cells
Guard cells are specialized plant cells in the epidermis of leaves, stems and other organs that are used to control gas exchange. They are produced in pairs with a gap between them that forms a stomatal pore. The stomatal pores are largest when water is freely available and the guard cells turgid, and closed when water availability is critically low and the guard cells become flaccid. Photosynthesis depends on the diffusion of carbon dioxide (CO2) from the air through the stomata into the mesophyll tissues. Oxygen (O2), produced as a byproduct of photosynthesis, exits the plant via the stomata. When the stomata are open, water is lost by evaporation and must be replaced via the transpiration stream, with water taken up by the roots. Plants must balance the amount of CO2 absorbed from the air with the water loss through the stomatal pores, and this is achieved by both active and passive control of guard cell turgor pressure and stomatal pore size.Schroeder JI, Kwak JM, & Allen G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asplenium Platyneuron
''Asplenium platyneuron'' (syn. ''Asplenium ebeneum''), commonly known as ebony spleenwort or brownstem spleenwort, is a fern native to North America east of the Rocky Mountains. It takes its common name from its dark, reddish-brown, glossy stipe and rachis (leaf stalk and midrib), which support 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. The species was first described in 1753 by Linnaeus as ''Acrostichum platyneuros'', although Linnaeus' type drew on material from several other species as well. It was more commonly called ''Asplenium ebeneum'', a name published by William Aiton in 1789, until the rediscovery and revival of the Linnaean epithet in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
