Huaraches are a type of Mexican sandal, Pre-Columbian in origin. Pre-Columbian in origin, the sandals are believed related to the cactle or cactli, of Náhuatl origin; the name "Huarache" is derived from the Purépecha language term kwarachi, directly translates into English as sandal. Early forms have been found in and traced to the countryside farming communities of Jalisco, Michoacan and Yucatan. Of all-leather construction, the thong structure around the main foot is still traditionally made with hand-woven braided leather straps. After originating in the peasant communities, they were adopted by some religious orders, such as the Franciscan friars. In the 1930s, wider variations began to appear, with soles derived from used rubber car tires—.hence the modern "tread" form of sole. Huaraches gained popularity in North America thanks to their adoption as part of the 1960s hippie lifestyle. By the end of the 20th century they were to be found all over South America. Traditional huarache designs vary but are always simple.
Made of all-leather early designs included woven string soles and thin wooden soles. More elaborate upper designs were created by saddlers and leather workers; the modern huarache developed from the adoption in the 1930s of rubber soles developed from used rubber car-tires. Modern designs vary in style from a simplistic sandal to a more complex shoe, using both traditional leather as well as more modern synthetic materials. Many shoes claim to be huaraches, but they are still traditionally only considered a huarache if they are handmade, have a woven-leather form in the upper. Huaraches are mentioned in the lyrics of the Beach Boys songs "Surfin' U. S. A." and "Noble Surfer". Skeeter Phelan wears a pair of the shoes, which her traditionalist Southern mother hates, in the Kathryn Stockett novel The Help. Doc Sportello, the detective from Thomas Pynchon's Inherent Vice, wears a pair of huaraches, he loses one shoe and finishes the adventure using only the other one. Dép lốp, Vietnamese footwear made from old tires Huarache Waraji Xero Shoes
Salento is a geographic region at the southern end of the administrative region of Apulia in Southern Italy. It is a sub-peninsula of the Italian Peninsula, sometimes described as the "heel" of the Italian "boot", it encompasses the entire administrative area of the province of Lecce, a large part of the province of Brindisi and part of that of Taranto. The peninsula is known as Terra d'Otranto, in the past Sallentina. In ancient times it was called variously Messapia. Messapia was the ancient name of a region of Italy corresponding to modern Salento, it was inhabited chiefly by the Messapii in classical times. Pokorny derives the toponym from the reconstructed PIE *medhyo-, "middle" and PIE *ap-, "water". Pokorny compares the toponym Messapia to another ancient Italic toponym, Salapia, "salt water", a city in Apulia. Salento peninsula is composed of limestone. Known as "peninsula salentina", from a geo-morphologic point of view it encompasses the land borders between Ionian and the Adriatic Seas, to the “Messapic threshold”, a depression that runs along the Taranto-Ostuni line and separates it from the Murge.
Its borders are: Taranto, in the Province of Taranto Pilone, in the territory of Ostuni, in the Province of Brindisi Santa Maria di Leuca, in the Province of Lecce. Acquarica del Capo, Alezio, Andrano, Arnesano, Bagnolo del Salento, Calimera, Campi Salentina, Caprarica di Lecce, Carpignano Salentino, Castri di Lecce, Castrignano de' Greci, Castrignano del Capo, Cavallino, Copertino, Corigliano d'Otranto, Cursi, Diso, Gagliano del Capo, Galatone, Giuggianello, Guagnano, Lequile, Lizzanello, Martano, Matino, Melissano, Miggiano, Minervino di Lecce, Monteroni di Lecce, Montesano Salentino, Morciano di Leuca, Muro Leccese, Nardò, Nociglia, Ortelle, Palmariggi, Patù, Porto Cesareo, Racale, Salice Salentino, San Cassiano, San Cesario di Lecce, San Donato di Lecce, San Pietro in Lama, Sannicola, Santa Cesarea Terme, Seclì, Sogliano Cavour, Specchia, Squinzano, Supersano, Surbo, Taviano, Trepuzzi, Tuglie, Uggiano la Chiesa, Vernole, Zollino. Brindisi, Cellino San Marco, Francavilla Fontana, Mesagne, Ostuni, San Donaci, San Michele Salentino, San Pancrazio Salentino, San Pietro Vernotico, San Vito dei Normanni, Torre Santa Susanna.
Avetrana, Faggiano, Grottaglie, Lizzano, Maruggio, Monteparano, Roccaforzata, San Giorgio Ionico, San Marzano di San Giuseppe, Torricella. Salento, from a cultural and linguistic point of view, does not include the city of Taranto, where the Tarantino dialect is spoken, nor the part of the province of Taranto to the west of the city, nor the rest of the province of Brindisi to north of Ostuni. To the south and east of the above areas, the Sicilian dialect of Salentino is spoken, as well as a Hellenic dialect known as Griko – a Greek variety; the nearest international airports are those of Bari. A 2-lane freeway connects Salento to Bari; the main railway line ends at Lecce. Other locations are served by regional railroads. Leisure ports are those of: Taranto, Campomarino di Maruggio's tourist and leisure Marina, Santa Maria di Leuca, Otranto; the coastal towers in Salento are coastal watchtowers, as the peninsula's coast was long subject to maritime attacks. The first towers may have been Norman.
The remaining historic towers are from the 15th and 16th centuries. Many are now in ruins. Media related to Coastal towers in Apulia at Wikimedia Commons Media related to Salento at Wikimedia Commons Salento travel guide from Wikivoyage
Sheffield is a city and metropolitan borough in South Yorkshire, England. Part of the West Riding of Yorkshire, its name derives from the River Sheaf, which runs through the city. With some of its southern suburbs annexed from Derbyshire, the city has grown from its industrial roots to encompass a wider economic base; the population of the City of Sheffield is 577,800 and it is one of the eight largest regional English cities that make up the Core Cities Group. Sheffield is the third-largest English district by population; the metropolitan population of Sheffield is 1,569,000. The city is in the eastern foothills of the Pennines, the valleys of the River Don and its four tributaries, the Loxley, the Porter Brook, the Rivelin and the Sheaf. Sixty-one per cent of Sheffield's entire area is green space, a third of the city lies within the Peak District national park. There are more than 250 parks and gardens in the city, estimated to contain around 4.5 million trees. Sheffield played a crucial role in the Industrial Revolution, with many significant inventions and technologies developed in the city.
In the 19th century, the city saw a huge expansion of its traditional cutlery trade, when stainless steel and crucible steel were developed locally, fuelling an tenfold increase in the population. Sheffield received its municipal charter in 1843, becoming the City of Sheffield in 1893. International competition in iron and steel caused a decline in these industries in the 1970s and 1980s, coinciding with the collapse of coal mining in the area; the 21st century has seen extensive redevelopment in Sheffield, along with other British cities. Sheffield's gross value added has increased by 60% since 1997, standing at £9.2 billion in 2007. The economy has experienced steady growth averaging around 5% annually, greater than that of the broader region of Yorkshire and the Humber; the city has a long sporting heritage, is home to the world's oldest football club, Sheffield F. C. Games between the two professional clubs, Sheffield United and Sheffield Wednesday, are known as the Steel City derby; the city is home to the World Snooker Championship and the Sheffield Steelers, the UK's first professional ice hockey team.
The area now occupied by the City of Sheffield is believed to have been inhabited since at least the late Upper Paleolithic, about 12,800 years ago. The earliest evidence of human occupation in the Sheffield area was found at Creswell Crags to the east of the city. In the Iron Age the area became the southernmost territory of the Pennine tribe called the Brigantes, it is this tribe who are thought to have constructed several hill forts around Sheffield. Following the departure of the Romans, the Sheffield area may have been the southern part of the Brittonic kingdom of Elmet, with the rivers Sheaf and Don forming part of the boundary between this kingdom and the kingdom of Mercia. Anglian settlers pushed west from the kingdom of Deira. A Britonnic presence within the Sheffield area is evidenced by two settlements called Wales and Waleswood close to Sheffield; the settlements that grew and merged to form Sheffield, date from the second half of the first millennium, are of Anglo-Saxon and Danish origin.
In Anglo-Saxon times, the Sheffield area straddled the border between the kingdoms of Mercia and Northumbria. The Anglo-Saxon Chronicle reports that Eanred of Northumbria submitted to Egbert of Wessex at the hamlet of Dore in 829, a key event in the unification of the kingdom of England under the House of Wessex. After the Norman conquest of England, Sheffield Castle was built to protect the local settlements, a small town developed, the nucleus of the modern city. By 1296, a market had been established at what is now known as Castle Square, Sheffield subsequently grew into a small market town. In the 14th century, Sheffield was noted for the production of knives, as mentioned in Geoffrey Chaucer's The Canterbury Tales, by the early 1600s it had become the main centre of cutlery manufacture in England outside London, overseen by the Company of Cutlers in Hallamshire. From 1570 to 1584, Queen of Scots, was imprisoned in Sheffield Castle and Sheffield Manor. During the 1740s, a form of the crucible steel process was discovered that allowed the manufacture of a better quality of steel than had been possible.
In about the same period, a technique was developed for fusing a thin sheet of silver onto a copper ingot to produce silver plating, which became known as Sheffield plate. These innovations spurred Sheffield's growth as an industrial town, but the loss of some important export markets led to a recession in the late 18th and early 19th century; the resulting poor conditions culminated in a cholera epidemic that killed 402 people in 1832. The population of the town grew throughout the 19th century; the Sheffield and Rotherham railway was constructed in 1838. The town was incorporated as a borough in 1842, was granted a city charter in 1893; the influx of people led to demand for better water supplies, a number of new reservoirs were constructed on the outskirts of the town. The collapse of the dam wall of one of these reservoirs in 1864 resulted in the Great Sheffield Flood, which killed 270 people and devastated large parts of the town; the growing population led to the construction of many back-to-back dwellings that, along with severe pollution from the factories, inspired George Orwell in 1937 to write: "Sheffield, I suppose, could justly claim to be called the ugliest town in the Old World".
The Great Depression hit the city in the 1930s, but as international tensions increased and the Second
High heels are a type of shoe in which the heel, compared with the toe, is higher off the ground. These shoes go beyond protecting the foot from the ground or improving efficiency of walking. High heels make the wearer taller, accentuating the length of the leg overall. There are many types of high heels, which come in different styles and materials, can be found all over the world, they have significant cultural and fashionable meanings attached to them, which have been shaped by historical contexts over the past 1,000 years. High heels have a rich history, dating as far back as the tenth century; the Persian cavalry, for example, wore a kind of boot with heels in order to ensure their feet stayed in the stirrups. Furthermore, research indicates that heels kept arrow-shooting riders, who stood up on galloping horses, safely on the horse; this trend has translated into the popular 21st-century cowboy boot. Owning horses was expensive and time-consuming, so to wear heels implied the wearer had significant wealth.
This practical and effective use of the heel has set the standard for most horse-back riding shoes throughout history and into the present day. In the 12th century, in India, heels become visible again; the image of a statue from the Ramappa Temple proves this, showing an Indian woman's foot clad in a raised shoe. During the Medieval period, both men and women wore platform shoes in order to raise themselves out of the trash and excrement filled streets. In 1430, chopines were 30 inches high, at times. Venetian law limited the height to three inches—but this regulation was ignored. A 17th-century law in Massachusetts announced that women would be subjected to the same treatment as witches if they lured men into marriage via the use of high-heeled shoes. Modern high heels were brought to Europe by emissaries of Shāh Abbās I of Persia in the early 17th century. Men wore them to imply their upper-class status. Royalty such as King Louis XIV wore heels to impart status; as the shoes caught on, other members of society began donning high heels, elite members ordered their heels to be made higher to distinguish themselves from lower classes.
Authorities began regulating the length of a high heel's point according to social rank. Klaus Carl includes these lengths in his book Shoes: "½ inch for commoners, 1 inch for the bourgeois, 1 and ½ inches for knights, 2 inches for nobles, 2 and ½ inches for princes."” As women took to appropriating this style, the heels’ width changed in another fundamental way. Men wore thick heels; when Enlightenment ideals such as science and logic took hold of many European societies, men stopped wearing heels. After the French Revolution in the late 1780s, heels and superficiality all became intertwined. In this way, heels became much more associated with a woman's supposed sense of impracticality and extravagance; the design of the high French heels from the late 1600s to around the 1720s placed body weight on the ball of the foot, were decorated with lace or braided fabric. From the 1730s-1740s, wide heels with an upturned toe and a buckle fastening became popular; the 1750s and 1760s introduced a skinnier, higher heel.
The 1790s added combinations of color. Additionally, throughout all of these decades, there was no difference between the right and left shoe. In Britain in 1770, an act was introduced into the parliament which would have applied the same penalties as witchcraft to the use of high heels and other cosmetic devices. Heels went out of fashion starting around 1810, in 1860 they returned at about two and a half inches; the Pinet heel and the Cromwell heel were both introduced during this time. Their production was increased with the invention and eventual mass production of the sewing machine around the 1850s. With sewing machines, yields increased as machines could and cheaply "position the heel, stitc the upper, attac the upper to the sole." This is a prime example of how the popularity of heels interacts with the culture and technology of the time. With the 1900s bringing two devastating world wars, many countries set wartime regulations for rationing all aspects of life; this included materials used for making heels, such as silk, rubber, or leather.
Another one of the numerous outcomes of these wars was an increase in international relations, a more proliferate sharing of fashion through photography and films, which helped spread high heel fashion as well. Examples of this were the brown and white pumps with cutouts or ankle straps combined with an open toe, their practicality yet professional look appealed to the fast-paced lifestyle of many women. Alternatively, World War II led to the popularization of pin-up girl posters, which men would hang in their bunks while at war. All of these girls were pictured wearing high heels, leading to an increase in the relationship between high heels and female sexuality; the tall, skinny stiletto heel was invented in 1950, strengthening the relationship between women and appearance. There was a weakening of the stiletto style during both the late 1960s / early 1970s and 1990s when block heels were more prominent, followed by a revival in the 2000s; the intricate and complex history of high heels has led to a variety of cultural thoughts and lens through which people view them today.
Firstly, it is exclusively gendered in the sense that few men wear high heels in present times. Secondly, magazines like Pla
Radiocarbon dating is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was developed in the late 1940s by Willard Libby, who received the Nobel Prize in Chemistry for his work in 1960, it is based on the fact that radiocarbon is being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting 14C combines with atmospheric oxygen to form radioactive carbon dioxide, incorporated into plants by photosynthesis; when the animal or plant dies, it stops exchanging carbon with its environment, from that point onwards the amount of 14C it contains begins to decrease as the 14C undergoes radioactive decay. Measuring the amount of 14C in a sample from a dead plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died; the older a sample is, the less 14C there is to be detected, because the half-life of 14C is about 5,730 years, the oldest dates that can be reliably measured by this process date to around 50,000 years ago, although special preparation methods permit accurate analysis of older samples.
Research has been ongoing since the 1960s to determine what the proportion of 14C in the atmosphere has been over the past fifty thousand years. The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's calendar age. Other corrections must be made to account for the proportion of 14C in different types of organisms, the varying levels of 14C throughout the biosphere. Additional complications come from the burning of fossil fuels such as coal and oil, from the above-ground nuclear tests done in the 1950s and 1960s; because the time it takes to convert biological materials to fossil fuels is longer than the time it takes for its 14C to decay below detectable levels, fossil fuels contain no 14C, as a result there was a noticeable drop in the proportion of 14C in the atmosphere beginning in the late 19th century. Conversely, nuclear testing increased the amount of 14C in the atmosphere, which attained a maximum in about 1965 of twice what it had been before the testing began.
Measurement of radiocarbon was done by beta-counting devices, which counted the amount of beta radiation emitted by decaying 14C atoms in a sample. More accelerator mass spectrometry has become the method of choice; the development of radiocarbon dating has had a profound impact on archaeology. In addition to permitting more accurate dating within archaeological sites than previous methods, it allows comparison of dates of events across great distances. Histories of archaeology refer to its impact as the "radiocarbon revolution". Radiocarbon dating has allowed key transitions in prehistory to be dated, such as the end of the last ice age, the beginning of the Neolithic and Bronze Age in different regions. In 1939, Martin Kamen and Samuel Ruben of the Radiation Laboratory at Berkeley began experiments to determine if any of the elements common in organic matter had isotopes with half-lives long enough to be of value in biomedical research, they synthesized 14C using the laboratory's cyclotron accelerator and soon discovered that the atom's half-life was far longer than had been thought.
This was followed by a prediction by Serge A. Korff employed at the Franklin Institute in Philadelphia, that the interaction of thermal neutrons with 14N in the upper atmosphere would create 14C, it had been thought that 14C would be more to be created by deuterons interacting with 13C. At some time during World War II, Willard Libby, at Berkeley, learned of Korff's research and conceived the idea that it might be possible to use radiocarbon for dating. In 1945, Libby moved to the University of Chicago, he published a paper in 1946 in which he proposed that the carbon in living matter might include 14C as well as non-radioactive carbon. Libby and several collaborators proceeded to experiment with methane collected from sewage works in Baltimore, after isotopically enriching their samples they were able to demonstrate that they contained 14C. By contrast, methane created from petroleum showed no radiocarbon activity because of its age; the results were summarized in a paper in Science in 1947, in which the authors commented that their results implied it would be possible to date materials containing carbon of organic origin.
Libby and James Arnold proceeded to test the radiocarbon dating theory by analyzing samples with known ages. For example, two samples taken from the tombs of two Egyptian kings and Sneferu, independently dated to 2625 BC plus or minus 75 years, were dated by radiocarbon measurement to an average of 2800 BC plus or minus 250 years; these results were published in Science in 1949. Within 11 years of their announcement, more than 20 radiocarbon dating laboratories had been set up worldwide. In 1960, Libby was awarded the Nobel Prize in Chemistry for this work. In nature, carbon exists as two stable, nonradioactive isotopes: carbon-12, carbon-13, a radioactive isotope, carbon-14 known as "radiocarbon"; the half-life
Artemisia tridentata called big sagebrush, Great Basin sagebrush or sagebrush, is an aromatic shrub from the family Asteraceae, which grows in arid and semi-arid conditions, throughout a range of cold desert and mountain habitats in the Intermountain West of North America. The vernacular name "sagebrush" is used for several related members of the genus Artemisia, such as California sagebrush. Big Sagebrush and other Artemisia shrubs are the dominant plant species across large portions of the Great Basin; the range extends northward through British Columbia's southern interior, south into Baja California, east into the western Great Plains of New Mexico, Colorado and the Dakotas. Several major threats exist to sage brush ecosystems, including human settlements, conversion to agricultural land, livestock grazing, invasive plant species and climate change. Sagebrush provides food and habitat for a variety of species, such as sage grouse, pronghorn antelope, grey vireo, pygmy rabbit, mule deer.
Artemisia tridentata is the state flower of Nevada. Much discussion and disagreement revolves around the question of how to divide the species into varieties and subgenera; the following subspecies are accepted by some authors. A. tridentata subsp. Tridentata A. tridentata subsp. Vaseyana A. tridentata subsp. Wyomingensis – Found in the drier portions of the sagebrush steppe. Shrub density is less than 1 plant/m2, with little herbaceous cover surrounding the shrub. A. tridentata subsp. Xericensis A. tridentata subsp. Spiciformis A. tridentata subsp. Parishii – Big sagebrush is a coarse, many-branched, pale-grey shrub with yellow flowers and silvery-grey foliage, 0.5–3 m tall. A deep taproot 1–4 m in length, coupled with laterally spreading roots near the surface, allows sagebrush to gather water from both surface precipitation and the water table several meters beneath. Big sagebrush, over a meter tall is an indicator of arable land, because it prefers deep, basic soils. Sagebrush is long-lived once it makes it past the seedling stage, can reach ages of over 100 years.
The species has a strong pungent fragrance due to the presence of camphor and other volatile oils. The taste is bitter and, together with the odor, serves to discourage browsing by many herbivores, it is an evergreen shrub. The leaves—attached to the branches at the axillary nodes—are wedge-shaped, 1–3 cm long and 0.3–1 cm broad, with the wider outer tips divided into three lobes. The leaves are covered with fine silvery hairs. Artemisia tridentata flowers in the late summer or early fall; the small yellow flowers are in long, loosely arranged tubular clusters. The fruits are seed-like, have a small amount of hairs on the surface; the Cahuilla used to gather large quantities of sagebrush seed, grind it to make flour. Big sagebrush can reproduce through sprouts, which shoot up from the underground rhizome; the sprouts are an extension of the parental plant while seedlings are individualistic to any other plant. Among these two strategies, the seedlings need more moisture for early survival; this is due to the sprouts being connected to healthy and associated plants while the new seedlings will start anew.
Artemisia tridentata grows in arid and semi-arid conditions, throughout the Intermountain West of North America. Sagebrush is not a desert plant, but rather a resident of the steppe, in areas that receive 18–40 centimeters of annual precipitation. Big sagebrush and other Artemisia species are the dominant plants across large portions of the Great Basin, covering some 422,000 square miles in 11 western U. S. states and Canadian provinces. Sagebrush provides food and habitat for a variety of animal species, such as sage grouse, grey vireo, pygmy rabbit, mule deer. Sagebrush creates habitat for many species of grasses and herbs. Besides providing shade and shelter from the wind, the long taproot of sagebrush draws water up from deep in the soil, some of which becomes available to these surrounding shallow-rooted plants; the terpenoid compounds in big sagebrush are thought to ward off herbivores. These oils, at high concentrations, are toxic to the symbiotic bacteria in the rumen of some ruminants like deer and cattle.
Pronghorn are the only large herbivore to browse sagebrush extensively. Damage to sagebrush plants caused by grazing herbivores results in the release of volatile chemicals, which are used to signal a warning to nearby plants, so that they can increase the production of repellent chemical compounds; this plant-to-plant communication can take place at distances of up to 60 cm. Several major threats exist to sage brush ecosystems, including human settlements, conversion to agricultural land, livestock grazing, invasive plant species and climate change; the cattle industry burns large areas of sagebrush habitat to make way for grazing animals. Due to large periods of time where sagebrush was the primary shrub, many species have become adapted to this habitat; the burning of the shrubs leads to habitat loss of many species and can be detrimental to the ecosystem as a whole. Furthermore, the destruction of native grasses and forbs by grazing and fire creates conditions where invasive plants colonize the area.
The invasive species which has destroyed the largest amount of sagebrush habitat is cheatgrass
Poaceae or Gramineae is a large and nearly ubiquitous family of monocotyledonous flowering plants known as grasses referred to collectively as grass. Poaceae includes the cereal grasses and the grasses of natural grassland and cultivated lawns and pasture. Grasses have stems that are hollow except at the nodes and narrow alternate leaves borne in two ranks; the lower part of each leaf encloses the stem. With around 780 genera and around 12,000 species, Poaceae are the fifth-largest plant family, following the Asteraceae, Orchidaceae and Rubiaceae. Grasslands such as savannah and prairie where grasses are dominant are estimated to constitute 40.5% of the land area of the Earth, excluding Greenland and Antarctica. Grasses are an important part of the vegetation in many other habitats, including wetlands and tundra; the Poaceae are the most economically important plant family, providing staple foods from domesticated cereal crops such as maize, rice and millet as well as forage, building materials and fuel.
Though they are called "grasses", seagrasses and sedges fall outside this family. The rushes and sedges are related to the Poaceae, being members of the order Poales, but the seagrasses are members of order Alismatales; the name Poaceae was given by John Hendley Barnhart in 1895, based on the tribe Poeae described in 1814 by Robert Brown, the type genus Poa described in 1753 by Carl Linnaeus. The term is derived from the Ancient Greek πόα. Grasses include some of the most versatile plant life-forms, they became widespread toward the end of the Cretaceous period, fossilized dinosaur dung have been found containing phytoliths of a variety that include grasses that are related to modern rice and bamboo. Grasses have adapted to conditions in lush rain forests, dry deserts, cold mountains and intertidal habitats, are the most widespread plant type. A cladogram shows subfamilies and approximate species numbers in brackets: Before 2005, fossil findings indicated that grasses evolved around 55 million years ago.
Recent findings of grass-like phytoliths in Cretaceous dinosaur coprolites have pushed this date back to 66 million years ago. In 2011, revised dating of the origins of the rice tribe Oryzeae suggested a date as early as 107 to 129 Mya. Wu, You & Li described grass microfossils extracted from a specimen of the hadrosauroid dinosaur Equijubus normani from the Early Cretaceous Zhonggou Formation; the authors noted that India became separated from Antarctica, therefore all other continents at the beginning of late Aptian, so the presence of grasses in both India and China during the Cretaceous indicates that the ancestor of Indian grasses must have existed before late Aptian. Wu, You & Li considered the Barremian origin for grasses to be probableThe relationships among the three subfamilies Bambusoideae and Pooideae in the BOP clade have been resolved: Bambusoideae and Pooideae are more related to each other than to Oryzoideae; this separation occurred within the short time span of about 4 million years.
According to Lester Charles King the spread of grasses in the Late Cenozoic would have changed patterns of hillslope evolution favouring slopes that are convex upslope and concave downslope and lacking a free face were common. King argued that this was the result of more acting surface wash caused by carpets of grass which in turn would have resulted in more soil creep. Grasses may be annual or perennial herbs with the following characteristics: The stems of grasses, called culms, are cylindrical and are hollow, plugged at the nodes, where the leaves are attached. Grass leaves are nearly always alternate and distichous, have parallel veins; each leaf is differentiated into a lower sheath hugging a blade with entire margins. The leaf blades of many grasses are hardened with silica phytoliths, which discourage grazing animals. A membranous appendage or fringe of hairs called the ligule lies at the junction between sheath and blade, preventing water or insects from penetrating into the sheath. Flowers of Poaceae are characteristically arranged in each having one or more florets.
The spikelets are further grouped into spikes. The part of the spikelet that bears the florets is called the rachilla. A spikelet consists of two bracts at called glumes, followed by one or more florets. A floret consists of the flower surrounded by two bracts, one external—the lemma—and one internal—the palea; the flowers are hermaphroditic—maize being an important exception—and anemophilous or wind-pollinated, although insects play a role. The perianth is reduced to two scales, called lodicules, that expand and contract to spread the lemma and palea; this complex structure can be seen in the image on the right. The fruit of grasses is a caryopsis. A tiller is a leafy shoot other than the first shoot produced from the seed. Grass blades grow at the base of the blade and not from elongated stem tips; this low growth point evolved in response to grazing animals and allows grasses to be grazed or mown without severe damage to the plant. Three general classifications of growth habit present in g