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Isoetes Eludens
''Isoetes eludens'' is an aquatic plant in the genus commonly known as quillwort that is native to the Kamiesberg Mountains in Namaqualand, South Africa. So far it is known to grow only in a single !gau (gnamma), a small temporary pool formed in a hollowed out area of granite rock. It has likely been growing in that region for millions of years, but was only discovered in 2007 and described in 2009. The specific epithet ''eludens'' refers to the fact that it eluded discovery, in spite of several searches in recent years in the area for new quillwort species. Description The genus ''Isoetes'', the quillworts, are most closely related to Selaginellas, with fossils morphologically similar to extant species dating back more than 150 million years. ''Isoetes eludens'' grows only tall, with root hairs growing under the soil surface. It has up to twelve green sporophylls, or leaves that produce spores, growing in a tight cluster. Like other quillworts, the sporophylls are hollow and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quillwort
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual species often scarce to rare. Some botanists split the genus, separating two South American species into the genus ''Stylites'', although molecular data place these species among other species of ''Isoetes'', so that ''Stylites'' does not warrant taxonomic recognition. Species of ''Isoetes'' virtually identical to modern forms have existed since the Jurassic epoch. The name of the genus may also be spelled ''Isoëtes''. The diaeresis (two dots over the e) indicates that the o and the e are to be pronounced in two distinct syllables. Including this in print is optional; either spelling (''Isoetes'' or ''Isoëtes'') is correct. Description Quillworts are mostly aquatic or semi-aquatic in clear ponds and slow-moving streams, though several ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megaspore
Megaspores, also called macrospores, are a type of spore that is present in heterosporous plants. These plants have two spore types, megaspores and microspores. Generally speaking, the megaspore, or large spore, germinates into a female gametophyte, which produces egg cells. These are fertilized by sperm produced by the male gametophyte developing from the microspore. Heterosporous plants include seed plants (gymnosperms and flowering plants), water ferns (Salviniales), spikemosses ( Selaginellaceae) and quillworts ( Isoetaceae). Megasporogenesis In gymnosperms and flowering plants, the megaspore is produced inside the nucellus of the ovule. During megasporogenesis, a diploid precursor cell, the megasporocyte or megaspore mother cell, undergoes meiosis to produce initially four haploid cells (the megaspores). Angiosperms exhibit three patterns of megasporogenesis: monosporic, bisporic, and tetrasporic, also known as the ''Polygonum'' type, the ''Alisma'' type, and the ''Drusa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vulnerable Species
A vulnerable species is a species which has been categorized by the International Union for Conservation of Nature as being threatened with extinction unless the circumstances that are threatening its survival and reproduction improve. Vulnerability is mainly caused by habitat loss or destruction of the species' home. Vulnerable habitat or species are monitored and can become increasingly threatened. Some species listed as "vulnerable" may be common in captivity, an example being the military macaw. There are currently 5196 animals and 6789 plants classified as Vulnerable, compared with 1998 levels of 2815 and 3222, respectively. Practices such as cryoconservation of animal genetic resources have been enforced in efforts to conserve vulnerable breeds of livestock specifically. Criteria The International Union for Conservation of Nature uses several criteria to enter species in this category. A taxon is Vulnerable when it is not critically endangered or Endangered but ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Botanic Gardens, Kew
Royal Botanic Gardens, Kew is a non-departmental public body in the United Kingdom sponsored by the Department for Environment, Food and Rural Affairs. An internationally important botanical research and education institution, it employs 1,100 staff. Its board of trustees is chaired by Dame Amelia Fawcett. The organisation manages botanic gardens at Kew in Richmond upon Thames in south-west London, and at Wakehurst, a National Trust property in Sussex which is home to the internationally important Millennium Seed Bank, whose scientists work with partner organisations in more than 95 countries. Kew, jointly with the Forestry Commission, founded Bedgebury National Pinetum in Kent in 1923, specialising in growing conifers. In 1994, the Castle Howard Arboretum Trust, which runs the Yorkshire Arboretum, was formed as a partnership between Kew and the Castle Howard Estate. In 2019, the organisation had 2,316,699 public visitors at Kew, and 312,813 at Wakehurst. Its site ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Union For Conservation Of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natural resources. It is involved in data gathering and analysis, research, field projects, advocacy, and education. IUCN's mission is to "influence, encourage and assist societies throughout the world to conserve nature and to ensure that any use of natural resources is equitable and ecologically sustainable". Over the past decades, IUCN has widened its focus beyond conservation ecology and now incorporates issues related to sustainable development in its projects. IUCN does not itself aim to mobilize the public in support of nature conservation. It tries to influence the actions of governments, business and other stakeholders by providing information and advice and through building partnerships. The organization is best known to the wider p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corm
A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat ( perennation). The word ''cormous'' usually means plants that grow from corms, parallel to the terms ''tuberous'' and ''bulbous'' to describe plants growing from tubers and bulbs. Structure A corm consists of one or more internodes with at least one growing point, generally with protective leaves modified into skins or tunics. The tunic of a corm forms from dead petiole sheaths—remnants of leaves produced in previous years. They act as a covering, protecting the corm from insects, digging animals, flooding, and water loss. The tunics of some species are thin, dry, and papery, at least in young plants, however, in some families, such as ''Iridaceae'', the tunic of a mature corm can be formidable protection. For example, some of the larger species of '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures and pressures than schist. Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct cleavage. Gneisses are common in the ancient crust of continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss. Description Orthogneiss from the Czech Republic In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding ( gneissic banding) but poorly developed schistosity and indistinct cleavage. In other words, it is a metamorphic rock composed of mineral grains easily seen with the unaided eye, which form obvious compositional layers, but which has only a weak tendency to fra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microspore
Microspores are land plant spores that develop into male gametophytes, whereas megaspores develop into female gametophytes. The male gametophyte gives rise to sperm cells, which are used for fertilization of an egg cell to form a zygote. Megaspores are structures that are part of the alternation of generations in many seedless vascular cryptogams, all gymnosperms and all angiosperms. Plants with heterosporous life cycles using microspores and megaspores arose independently in several plant groups during the Devonian period. Microspores are haploid, and are produced from diploid microsporocytes by meiosis. Morphology The microspore has three different types of wall layers. The outer layer is called the perispore, the next is the exospore, and the inner layer is the endospore. The perispore is the thickest of the three layers while the exospore and endospore are relatively equal in width. Seedless vascular plants In heterosporous seedless vascular plants, modified leaves ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quill
A quill is a writing tool made from a moulted flight feather (preferably a primary wing-feather) of a large bird. Quills were used for writing with ink before the invention of the dip pen, the metal- nibbed pen, the fountain pen, and, eventually, the ballpoint pen. As with the earlier reed pen (and later dip pen), a quill has no internal ink reservoir and therefore needs to periodically be dipped into an inkwell during writing. The hand-cut goose quill is rarely used as a calligraphy tool anymore because many papers are now derived from wood pulp and would quickly wear a quill down. However, it is still the tool of choice for a few scribes who have noted that quills provide an unmatched sharp stroke as well as greater flexibility than a steel pen. Description The shaft of a flight feather is long and hollow, making it an obvious candidate for being crafted into a pen. The process of making a quill from a feather involves curing the shaft to harden it, then fashioning it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kamiesberge
The Kamiesberg or Kamiesberge (Khoikhoi ''"Th'amies"'' = ''"jumble"''), is a mountain range of jumbled granite inselbergs or bornhardts dotted over sandy plains and centered on Kamieskroon in Namaqualand in South Africa. This range is very like the Matopos of Zimbabwe in appearance. It stretches for about 140 km (60 mi) from Garies in the south to Springbok in the north and forms a plateau between the Sandveld of the Cape West Coast and Bushmanland in the east, with the Hardveld of the mountainous central Kamiesberg escarpment in the midst. History The region was formerly occupied by Khoikhoi who were nomadic pastoralists. The buildings of Kamieskroon were moved from a previous location known as Bowesdorp, named after the village doctor. Steep granite hills and a shortage of water hindered development, so that it was relocated. The foundations of the original village may still be seen in a rocky ravine some 8 km north of Kamieskroon. The Leliefontein mission ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, fungi and protozoa. Bacterial spores are not part of a sexual cycle, but are resistant structures used for survival under unfavourable conditions. Myxozoan spores release amoeboid infectious germs ("amoebulae") into their hosts for parasitic infection, but also reproduce within the hosts through the pairing of two nuclei within the plasmodium, which develops from the amoebula. In plants, spores are usually haploid and unicellular and are produced by meiosis in the sporangium of a diploid sporophyte. Under favourable conditions the spore can develop into a new organism using mitotic division, producing a multicellular gametophyte, which eventually goes on to produce gametes. Two gametes fuse to form a zygote which develops into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sporophyll
A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls (whether they are microphylls or megaphylls) bear either megasporangia and thus are called megasporophylls, or microsporangia and are called microsporophylls. The overlap of the prefixes and roots makes these terms a particularly confusing subset of botanical nomenclature. Sporophylls vary greatly in appearance and structure, and may or may not look similar to sterile leaves. Plants that produce sporophylls include: ''Alaria esculenta'', a brown alga which shows sporophylls attached near the base of the alga.Dickson, Carola I. 1963. ''British Seaweeds''. The Kew Series. Lycophytes, where sporophylls may be aggregated into strobili (''Selaginella'' and some ''Lycopodium'' and related genera) or distributed singly among sterile leaves ('' Huperzia''). Sporangia are borne in the axil or on the adaxial surface of the sporophyll. In heterosporous memb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
