Asclepias is a genus of herbaceous, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic; the genus contains over 200 species distributed broadly across Africa, North America, South America. It belonged to the family Asclepiadaceae, now classified as the subfamily Asclepiadoideae of the dogbane family Apocynaceae; the genus was formally described by Carl Linnaeus in 1753, who named it after Asclepius, the Greek god of healing. Members of the genus Asclepias produce some of the most complex flowers in the plant kingdom, comparable to orchids in complexity. Five petals reflex backwards revealing a gynostegium surrounded by a five-membrane corona; the corona is composed of a five paired hood and horn structure with the hood acting as a sheath for the inner horn. Glands holding pollinia are found between the hoods; the size and color of the horns and hoods are important identifying characteristics for species in the genus Asclepias.
Pollination in this genus is accomplished in an unusual manner. Pollen is grouped into complex structures called pollinia, rather than being individual grains or tetrads, as is typical for most plants; the feet or mouthparts of flower-visiting insects such as bees and butterflies, slip into one of the five slits in each flower formed by adjacent anthers. The bases of the pollinia mechanically attach to the insect, so that a pair of pollen sacs can be pulled free when the pollinator flies off, assuming the insect is large enough to produce the necessary pulling force. Pollination is effected by the reverse procedure, in which one of the pollinia becomes trapped within the anther slit. Large-bodied hymenopterans are the most common and best pollinators, whereas monarch butterflies are not good pollinators of milkweed. Asclepias species produce their seeds in pods termed follicles; the seeds, which are arranged in overlapping rows, bear a cluster of white, filament-like hairs known as the coma. The follicles ripen and split open, the seeds, each carried by its coma, are blown by the wind.
Some, but not all, milkweeds reproduced by clonal reproduction. American milkweeds are an important nectar source for native bees and other nectar-seeking insects, though non-native honey bees get trapped in the stigmatic slits and die. Milkweeds are the larval food source for monarch butterflies and their relatives, as well as a variety of other herbivorous insects specialized to feed on the plants despite their chemical defenses. Milkweeds use three primary defenses to limit damage caused by caterpillars: hairs on the leaves, cardenolide toxins, latex fluids. Data from a DNA study indicate that more evolved milkweed species use these preventative strategies less but grow faster than older species regrowing faster than caterpillars can consume them. Milkweed is not grown commercially in large scale, but the plant has had many uses throughout human history; the milkweed filaments from the coma are hollow and coated with wax, have good insulation qualities. During World War II, more than 5,000 t of milkweed floss was collected in the United States as a substitute for kapok.
Milkweed is grown commercially as a hypoallergenic filling for pillows and as insulation for winter coats. A study of the insulative properties of various materials found that milkweed floss was outperformed by other materials in terms of insulation and lumpiness, but it scored well when mixed with down feathers. Milkweed fibers are used to clean up oil spills; the bast fibers of some species can be used for rope. Milkweed latex contains about two percent latex and was attempted as a source of natural rubber by both Nazi Germany and the United States during World War II. No record has been found of large-scale success. Asclepias is known as "Silk of America", a strand of common milkweed gathered in the valley of the Saint Lawrence River in Canada; the silk is used in thermal insulation, acoustic insulation, oil absorbents. Milkweed contains cardiac glycoside poisons that inhibit animal cells from maintaining a proper K+, Ca+ concentration gradient; as a result, many natives of South America and Africa used arrows poisoned with these glycosides to fight and hunt more effectively.
Milkweed may cause death when animals consume large quantities of the plant. Milkweed causes mild dermatitis in some who come in contact with it. Nonetheless, it can be made edible; the leaves of Asclepias species are a food source for monarch butterfly larvae and some other milkweed butterflies. These plants are used in butterfly gardening; some Asclepias species: There are 12 species of Asclepias in South America, among them: A. barjoniifolia, A. boliviensis, A. curassavica, A. mellodora, A. candida, A. flava, A. pilgeriana. Species classified under the genus Asclepias include: Calotropis gigantea W. T. Aiton Calotropis procera W. T. Aiton Cynanchum louiseae Kartesz & Gandhi Cynanchum thesioides K. Schum. Funastrum clausum Schltr. Gomphocarpus cancellatus Bruyns Gomphocarpus fruticosus W. T. Aiton Marsdenia macrophylla E. Fourn. (as A. macrophylla Humb. &
The Cyperaceae are a family of graminoid, monocotyledonous flowering plants known as sedges, which superficially resemble the related rushes and the more distantly related grasses. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus Carex with over 2,000 species; these species are distributed, with the centers of diversity for the group occurring in tropical Asia and tropical South America. While sedges may be found growing in all environments, many are associated with wetlands, or with poor soils. Ecological communities dominated by sedges are known as sedgelands. Features distinguishing members of the sedge family from grasses or rushes are stems with triangular cross-sections and leaves that are spirally arranged in three ranks; some well-known sedges include the water chestnut and the papyrus sedge, from which the writing material papyrus was made. This family includes cotton-grass, spike-rush, nutsedge or nutgrass, white star sedge.
Cyperaceae at The Plant List Cyperaceae at The Families of Flowering Plants Cyperaceae at the Encyclopedia of Life Cyperaceae at the Angiosperm Phylogeny Website Cyperaceae at the Royal Botanic Gardens, Kew Cyperaceae at the online Flora of North America Cyperaceae at the online Flora of Michigan Cyperaceae at the online Flora of Northern Ireland Cyperaceae at the online Flora of Zimbabwe Cyperaceae at the online Flora of Western Australia Cyperaceae at the online Flora of New South Wales Cyperaceae at the online Flora of New Zealand Cyperaceae at Flowers in Israel
The Ancient Greek language includes the forms of Greek used in Ancient Greece and the ancient world from around the 9th century BCE to the 6th century CE. It is roughly divided into the Archaic period, Classical period, Hellenistic period, it is succeeded by medieval Greek. Koine is regarded as a separate historical stage of its own, although in its earliest form it resembled Attic Greek and in its latest form it approaches Medieval Greek. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects. Ancient Greek was the language of Homer and of fifth-century Athenian historians and philosophers, it has contributed many words to English vocabulary and has been a standard subject of study in educational institutions of the Western world since the Renaissance. This article contains information about the Epic and Classical periods of the language. Ancient Greek was a pluricentric language, divided into many dialects; the main dialect groups are Attic and Ionic, Aeolic and Doric, many of them with several subdivisions.
Some dialects are found in standardized literary forms used in literature, while others are attested only in inscriptions. There are several historical forms. Homeric Greek is a literary form of Archaic Greek used in the epic poems, the "Iliad" and "Odyssey", in poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic and other Classical-era dialects; the origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period, they differ in some of the detail. The only attested dialect from this period is Mycenaean Greek, but its relationship to the historical dialects and the historical circumstances of the times imply that the overall groups existed in some form. Scholars assume that major Ancient Greek period dialect groups developed not than 1120 BCE, at the time of the Dorian invasion—and that their first appearances as precise alphabetic writing began in the 8th century BCE.
The invasion would not be "Dorian" unless the invaders had some cultural relationship to the historical Dorians. The invasion is known to have displaced population to the Attic-Ionic regions, who regarded themselves as descendants of the population displaced by or contending with the Dorians; the Greeks of this period believed there were three major divisions of all Greek people—Dorians and Ionians, each with their own defining and distinctive dialects. Allowing for their oversight of Arcadian, an obscure mountain dialect, Cypriot, far from the center of Greek scholarship, this division of people and language is quite similar to the results of modern archaeological-linguistic investigation. One standard formulation for the dialects is: West vs. non-west Greek is the strongest marked and earliest division, with non-west in subsets of Ionic-Attic and Aeolic vs. Arcadocypriot, or Aeolic and Arcado-Cypriot vs. Ionic-Attic. Non-west is called East Greek. Arcadocypriot descended more from the Mycenaean Greek of the Bronze Age.
Boeotian had come under a strong Northwest Greek influence, can in some respects be considered a transitional dialect. Thessalian had come under Northwest Greek influence, though to a lesser degree. Pamphylian Greek, spoken in a small area on the southwestern coast of Anatolia and little preserved in inscriptions, may be either a fifth major dialect group, or it is Mycenaean Greek overlaid by Doric, with a non-Greek native influence. Most of the dialect sub-groups listed above had further subdivisions equivalent to a city-state and its surrounding territory, or to an island. Doric notably had several intermediate divisions as well, into Island Doric, Southern Peloponnesus Doric, Northern Peloponnesus Doric; the Lesbian dialect was Aeolic Greek. All the groups were represented by colonies beyond Greece proper as well, these colonies developed local characteristics under the influence of settlers or neighbors speaking different Greek dialects; the dialects outside the Ionic group are known from inscriptions, notable exceptions being: fragments of the works of the poet Sappho from the island of Lesbos, in Aeolian, the poems of the Boeotian poet Pindar and other lyric poets in Doric.
After the conquests of Alexander the Great in the late 4th century BCE, a new international dialect known as Koine or Common Greek developed based on Attic Greek, but with influence from other dialects. This dialect replaced most of the older dialects, although Doric dialect has survived in the Tsakonian language, spoken in the region of modern Sparta. Doric has passed down its aorist terminations into most verbs of Demotic Greek. By about the 6th century CE, the Koine had metamorphosized into Medieval Greek. Ancient Macedonian was an Indo-European language at least related to Greek, but its exact relationship is unclear because of insufficient data: a dialect of Greek; the Macedonian dialect (or l
The flowering plants known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 64 orders, 416 families 13,164 known genera and c. 369,000 known species. Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, the production of fruits that contain the seeds. Etymologically, angiosperm means a plant; the term comes from the Greek words sperma. The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago, the first flowering plants are known from 160 mya, they diversified extensively during the Early Cretaceous, became widespread by 120 mya, replaced conifers as the dominant trees from 100 to 60 mya. Angiosperms differ from other seed plants in several ways, described in the table below; these distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.
Angiosperm stems are made up of seven layers. The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms; the vascular bundles of the stem are arranged such that the phloem form concentric rings. In the dicotyledons, the bundles in the young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles, a complete ring is formed, a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside; the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.
Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue. They once formed the stem increases in diameter only in exceptional cases; the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, provide the most trustworthy external characteristics for establishing relationships among angiosperm species; the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally from the axil of a leaf; as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More the flower-bearing portion of the plant is distinguished from the foliage-bearing or vegetative portion, forms a more or less elaborate branch-system called an inflorescence. There are two kinds of reproductive cells produced by flowers. Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens.
The "female" cells called megaspores, which will divide to become the egg cell, are contained in the ovule and enclosed in the carpel. The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators; the individual members of these surrounding structures are known as petals. The outer series is green and leaf-like, functions to protect the rest of the flower the bud; the inner series is, in general, white or brightly colored, is more delicate in structure. It functions to attract bird pollinators. Attraction is effected by color and nectar, which may be secreted in some part of the flower; the characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans. While the majority of flowers are perfect or hermaphrodite, flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization.
Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot transfer pollen to the pistil. Homomorphic flowers may employ a biochemical mechanism called self-incompatibility to discriminate between self and non-self pollen grains. In other species, the male and female parts are morphologically separated, developing on different flowers; the botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon and σπέρμα, was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked; the term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any
United States Department of Agriculture
The United States Department of Agriculture known as the Agriculture Department, is the U. S. federal executive department responsible for developing and executing federal laws related to farming and food. It aims to meet the needs of farmers and ranchers, promote agricultural trade and production, work to assure food safety, protect natural resources, foster rural communities and end hunger in the United States and internationally. 80% of the USDA's $141 billion budget goes to the Food and Nutrition Service program. The largest component of the FNS budget is the Supplemental Nutrition Assistance Program, the cornerstone of USDA's nutrition assistance; the current Secretary of Agriculture is Sonny Perdue. Many of the programs concerned with the distribution of food and nutrition to people of America and providing nourishment as well as nutrition education to those in need are run and operated under the USDA Food and Nutrition Service. Activities in this program include the Supplemental Nutrition Assistance Program, which provides healthy food to over 40 million low-income and homeless people each month.
USDA is a member of the United States Interagency Council on Homelessness, where it is committed to working with other agencies to ensure these mainstream benefits are accessed by those experiencing homelessness. The USDA is concerned with assisting farmers and food producers with the sale of crops and food on both the domestic and world markets, it plays a role in overseas aid programs by providing surplus foods to developing countries. This aid can go through USAID, foreign governments, international bodies such as World Food Program, or approved nonprofits; the Agricultural Act of 1949, section 416 and Agricultural Trade Development and Assistance Act of 1954 known as Food for Peace, provides the legal basis of such actions. The USDA is a partner of the World Cocoa Foundation. Early in its history, the economy of the United States was agrarian. Officials in the federal government had long sought new and improved varieties of seeds and animals for import into the United States. In 1837 Henry Leavitt Ellsworth, a Yale-educated attorney interested in improving agriculture, became Commissioner of Patents, a position within the Department of State.
He began collecting and distributing new varieties of seeds and plants through members of the Congress and agricultural societies. In 1839, Congress established the Agricultural Division within the Patent Office and allotted $1,000 for "the collection of agricultural statistics and other agricultural purposes." Ellsworth's interest in aiding agriculture was evident in his annual reports that called for a public depository to preserve and distribute the new seeds and plants, a clerk to collect agricultural statistics, statewide reports about crops in different regions, the application of chemistry to agriculture. Ellsworth was called the "Father of the Department of Agriculture."In 1849, the Patent Office was transferred to the newly created Department of the Interior. In the ensuing years, agitation for a separate bureau of agriculture within the department or a separate department devoted to agriculture kept recurring. On May 15, 1862, Abraham Lincoln established the independent Department of Agriculture to be headed by a commissioner without Cabinet status, the agriculturalist Isaac Newton was appointed to be the first such commissioner.
Lincoln called it the "people's department." In 1868, the Department moved into the new Department of Agriculture Building in Washington, D. C. designed by famed DC architect Adolf Cluss. Located on Reservation No.2 on the National Mall between 12th Street and 14th SW, the Department had offices for its staff and the entire width of the Mall up to B Street NW to plant and experiment with plants. In the 1880s, varied advocacy groups were lobbying for Cabinet representation. Business interests sought a Department of Commerce and Industry, farmers tried to raise the Department of Agriculture to Cabinet rank. In 1887, the House of Representatives and Senate passed bills giving Cabinet status to the Department of Agriculture and Labor, but the bill was defeated in conference committee after farm interests objected to the addition of labor. On February 9, 1889, President Grover Cleveland signed a bill into law elevating the Department of Agriculture to Cabinet level. In 1887, the Hatch Act provided for the federal funding of agricultural experiment stations in each state.
The Smith-Lever Act of 1914 funded cooperative extension services in each state to teach agriculture, home economics, other subjects to the public. With these and similar provisions, the USDA reached out to every county of every state. During the Great Depression, farming remained a common way of life for millions of Americans; the Department of Agriculture's Bureau of Home Economics, established in 1923, published shopping advice and recipes to stretch family budgets and make food go farther. USDA helped ensure that food continued to be produced and distributed to those who needed it, assisted with loans for small landowners, contributed to the education of the rural youth, it was revealed on August 27th, 2018 that the U. S. Department of Agriculture would be providing U. S. farmers with a farm aid package, which will total $4.7 billion in direct payments to American farmers. This package is meant to offset the losses farmers are expected to incur from retaliatory tariffs placed on American exports during the Trump tariffs.
The Department of Agriculture was authorized a budget for Fiscal Year 2015 of $139.7 billion. The budget authorization is broken down as follows: Agricultural Stabilization and Conservation Service Animal Damage Control (
A daylily is a flowering plant in the genus Hemerocallis. Gardening enthusiasts and professional horticulturalists have long bred daylily species for their attractive flowers. Thousands of cultivars have been registered by local and international Hemerocallis societies. Hemerocallis is now placed in family Asphodelaceae, subfamily Hemerocallidoideae, but used to be part of Liliaceae; the name Hemerocallis comes from the Greek words ἡμέρα "day" and καλός "beautiful". Daylilies are perennial plants, whose name alludes to the flowers which last no more than 24 hours; the flowers of most species open in early morning and wither during the following night replaced by another one on the same scape the next day. Some species are night-blooming. Daylilies are not used as cut flowers for formal flower arranging, yet they make good cut flowers otherwise as new flowers continue to open on cut stems over several days. Hemerocallis is native to Asia eastern Asia, including China and Japan; this genus is popular worldwide because of the showy hardiness of many kinds.
There are over 80,000 registered cultivars. Hundreds of cultivars have fragrant flowers, more scented cultivars are appearing more in northern hybridization programs; some earlier blooming cultivars rebloom in the season if their capsules, in which seeds are developing, are removed. Most kinds of daylilies occur as clumps, each of which has leaves, a crown and roots; the long, linear lanceolate leaves are grouped into opposite fans with arching leaves. The crown is the small white portion between the roots. Along the scape of some kinds of daylilies, small leafy "proliferations" form in bracts. A proliferation forms roots when planted and is an exact clone of its parent plant. Many kinds of daylilies have thickened roots in which they store water. A normal, single daylily flower has three petals and three sepals, collectively called tepals, each with a midrib in either the same basic color or a different color; the centermost part of the flower, called the throat is of a different color than the more distal areas of the tepals.
Each flower has six stamens, each with a two-lobed anther. After successful pollination, a flower forms a botanical capsule; the orange or tawny daylily, common along roadsides in much of the United States, is native to Asia and regarded as an invasive in North America. Hemerocallis species are toxic to cats and ingestion may be fatal. Treatment is successful if started before renal failure has developed; the World Checklist of Selected Plant Families recognizes 19 species as of September 2014: Hemerocallis citrina Baroni - China, Korea, Russian Far East Hemerocallis coreana Nakai - Japan, Shandong Province in China Hemerocallis darrowiana S. Y. Hu - Sakhalin Island in Russia Hemerocallis dumortieri E. Morren - China, Korea Hemerocallis esculenta Koidz. >) - China, Russian Far East Hemerocallis forrestii Diels - Sichuan + Yunnan Provinces in China Hemerocallis fulva L. – orange daylily, tawny daylily, tiger lily, ditch lily - China, Korea. G. Chung & S. S. Kang - Hongdo Islands of South Korea Hemerocallis lilioasphodelus L. – lemon lily, yellow daylily - China, Russian Far East, Kazakhstan.
& C. A. Mey. - China, Korea, Russian Far East Hemerocallis minor Mill. - China, Korea, Russian Far East, Siberia Hemerocallis multiflora Stout - Henan Province in China Hemerocallis nana W. W. Sm. & Forrest - Yunnan Province in China Hemerocallis plicata Stapf - Sichuan + Yunnan Provinces in China Hemerocallis taeanensis S. S. Kang & M. G. Chung - Korea Hemerocallis thunbergii Barr - Japan Hemerocallis yezoensis H. Hara - Japan, Kuril IslandsTwo hybrids are recognized: A number of hybrid names appear in the horticultural literature but are not recognized as valid by the World Checklist of Selected Plant Families; these include: The daylily is referred to as "the perfect perennial" by gardeners, due to its brilliant colors, ability to tolerate drought and frost and to thrive in many different climate zones, low maintenance. It is a vigorous perennial that lasts for many years in a garden, with little care and adapts to many different soil and light conditions. Daylilies have a short blooming period, depending on the type.
Some will bloom in early spring while others wait until the summer or autumn. Most daylily plants bloom for 1 through 5 weeks, although some bloom twice in one season"; the Orange Daylily, the sweet-scented Lemon-lily were early imports from England to 17th-century American gardens and soon escaped from gardens. The introduced Orange Daylily, although not a true lily, is now common in many natural areas, where it is considered an invasive. Hemerocallis lilioasphodelus gained the Royal Horticultural Society's Award of Garden
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