x̄ - > A flower part 1

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants. The biological function of a flower is to facilitate reproduction, usually by providing a mechanism for the union of sperm with eggs. Flowers may facilitate outcrossing resulting from cross-pollination or allow selfing when self-pollination occurs. The two types of pollination are self-pollination and cross-pollination. Self-pollination happens when the pollen from the anther is deposited on the stigma of the same flower, or another flower on the same plant. Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same species. Self-pollination happens in flowers where the stamen and carpel mature at the same time, and are positioned so that the pollen can land on the flower's stigma. This pollination does not require an investment from the plant to provide nectar and pollen as food for pollinators. Some flowers produce diaspores without fertilization. Flowers contain sporangia and are the site where gametophytes develop. Many flowers have evolved to be attractive to animals, so as to cause them to be vectors for the transfer of pollen. After fertilization, the ovary of the flower develops into fruit-containing seeds. In addition to facilitating the reproduction of flowering plants, flowers have long been admired and used by humans to bring beauty to their environment, and also as objects of romance, ritual, esotericism, witchcraft, religion, medicine, and as a source of food. Etymology Flower is from the Middle English flour, which referred to both the ground grain and the reproductive structure in plants, before splitting off in the 17th century. It comes originally from the Latin name of the Italian goddess of flowers, Flora. The early word for flower in English was blossom, though it now refers to flowers only of fruit trees. Morphology Parts The flower has two essential parts: the vegetative part, consisting of petals and associated structures in the perianth, and the reproductive or sexual parts. A stereotypical flower consists of four kinds of structures attached to the tip of a short stalk. Each of these kinds of parts is arranged in a whorl on the receptacle. The four main whorls are as follows: Perianth Collectively the calyx and corolla form the perianth. Calyx: The calyx consists of leaf-like structures at the base of a flower that protects the flower during development. The leaf-like structures are individually referred to as sepals. There are often as many of these sepals as there are petals. While most calyces are green, there are exceptions in which the calyx is the same color as the petals of the flower or a different color altogether. The calyx performs a crucial role for the flowering plant. As the flower is forming, it is closed tightly into a bud. The sepals are the outer covering of the flower as it forms and is the only thing you see of the flower while it is still in bud form. It protects the developing flower and prevents it from drying out. Corolla: the next whorl toward the apex, composed of units called petals, which are typically thin, soft, and colored to attract animals that help the process of pollination. 

Perigone: in monocots, the calyx and corolla are indistinguishable thus the whorls of the perianth or perigone are called tepals. Reproductive Androecium: the next whorl, consisting of units called stamens. Stamens consist of two parts: a stalk called a filament, topped by an anther where pollen is produced by meiosis and eventually dispersed. Gynoecium: the innermost whorl of a flower, consisting of one or more units called carpels. The carpel or multiple fused carpels form a hollow structure called an ovary, which produces ovules internally. Ovules are megasporangia and they, in turn, produce megaspores by meiosis which develop into female gametophytes. These give rise to egg cells. The gynoecium of a flower is also described using an alternative terminology wherein the structure one sees in the innermost whorl is called a pistil. A pistil may consist of a single carpel or a number of carpels fused together. The sticky tip of the pistil, the stigma, is the receptor of pollen. The supportive stalk, the style, becomes the pathway for pollen tubes to grow from pollen grains adhering to the stigma. The relationship to the gynoecium on the receptacle is described as hypogynous, perigynous, or epigynous. Structure Although the arrangement described above is considered "typical", plant species show a wide variation in floral structure. These modifications have significance in the evolution of flowering plants and are used extensively by botanists to establish relationships among plant species. The four main parts of a flower are generally defined by their positions on the receptacle and not by their function. Many flowers lack some parts or parts that may be modified into other functions and/or look like what is typically another part. In some families, like Ranunculaceae, the petals are greatly reduced and in many species, the sepals are colorful and petal-like. Other flowers have modified stamens that are petal-like; the double flowers of Peonies and Roses are mostly petaloid stamens. Flowers show great variation and plant scientists describe this variation in a systematic way to identify and distinguish species. Specific terminology is used to describe flowers and their parts. Many flower parts are fused together, fused parts originating from the same whorl are connate, while fused parts originating from different whorls are adnate; parts that are not fused are free. When petals are fused into a tube or ring that falls away as a single unit, they are sympetalous. Connate petals may have distinctive regions: the cylindrical base is the tube, the expanding region is the throat and the flaring outer region is the limb. A sympetalous flower, with bilateral symmetry with an upper and lower lip, is bilabiate. Flowers with connate petals or sepals may have various shaped corolla or calyx, including campanulate, funnelform, tubular, urceolate, salverform, or rotate. Referring to "fusion," as it is commonly done, appears questionable because at least some of the processes involved may be non-fusion processes. For example, the addition of intercalary growth at or below the base of the primordia of floral appendages such as sepals, petals, stamens, and carpels may lead to a common base that is not the result of fusion. Many flowers have some form of symmetry. When the perianth is bisected through the central axis from any point and symmetrical halves are produced, the flower is said to be actinomorphic or regular, e.g. rose or trillium. This is an example of radial symmetry. When flowers are bisected and produce only one line that produces symmetrical halves, the flower is said to be irregular or zygomorphic, e.g. snapdragon or most orchids Flowers may be directly attached to the plant at their base. The stem or stalk subtending a flower is called a peduncle. If a the peduncle supports more than one flower, the stems connecting each flower to the main axis are called pedicels. The apex of a flowering stem forms a terminal swelling which is called the torus or receptacle Inflorescence In those species that have more than one flower on an axis, the collective cluster of flowers is termed an inflorescence. Some inflorescences are composed of many small flowers arranged in a formation that resembles a single flower. The common example of this is most members of the very large composite group. A single daisy or sunflower, for example, is not a flower but a flower head—an inflorescence composed of numerous flowers. An inflorescence may include specialized stems and modified leaves known as bracts. Diagrams and formulae A floral formula is a way to represent the structure of a flower using specific letters, numbers, and symbols, presenting substantial information about the flower in a compact form. It can represent a taxon, usually giving ranges of the numbers of different organs or particular species. Floral formulae have been developed in the early 19th century and their use has declined since. Prenner et al. devised an extension of the existing model to broaden the descriptive capability of the formula. The format of floral formulae differs in different parts of the world, yet they convey the same information The structure of a flower can also be expressed by the means of floral diagrams. The use of schematic diagrams can replace long descriptions or complicated drawings as a tool for understanding both floral structure and evolution. Such diagrams may show important features of flowers, including the relative positions of the various organs, including the presence of fusion and symmetry, as well as structural details. Detailed developmental studies, however, have shown that stamens are often initiated more or less like modified stems that in some cases may even resemble branchlets. Transition The transition to flowering is one of the major phase changes that a plant makes during its life cycle. The transition must take place at a time that is favorable for fertilization and the formation of seeds, hence ensuring maximal reproductive success. To meet these needs a plant is able to interpret important endogenous and environmental cues such as changes in levels of plant hormones and seasonable temperature and photoperiod changes. Many perennial and most biennial plants require vernalization to flower. The molecular interpretation of these signals is through the transmission of a complex signal known as florigen, which involves a variety of genes, including Constans, Flowering Locus C and Flowering Locus T. Florigen is produced in the leaves in reproductively favorable conditions and acts in buds and growing tips to induce a number of different physiological and morphological changes. The first step of the transition is the transformation of the vegetative stem primordia into floral primordia. This occurs as biochemical changes take place to change cellular differentiation of leaf bud and stem tissues into tissue that will grow into the reproductive organs. Growth of the central part of the stem tip stops or flattens out and the sides develop protuberances in a whorled or spiral fashion around the outside of the stem end. These protuberances develop into the sepals, petals, stamens, and carpels. Once this process begins, in most plants, it cannot be reversed and the stems develop flowers, even if the initial start of the flower formation event was dependent of some environmental cue. Organ development The ABC model is a simple model that describes the genes responsible for the development of flowers. Three gene activities interact in a combinatorial manner to determine the developmental identities of the primordia organ within the floral apical meristem. These gene functions are called A. B, and C. A genes are expressed in only outer and lower most section of the apical meristem, which becomes a whorl of sepals. In the second whorl both A and B genes are expressed, leading to the formation of petals. In the third whorl, B and C genes interact to form stamens and in the center of the flower C genes alone give rise to carpels. The model is based upon studies of aberrant flowers and mutations in Arabidopsis thaliana and the snapdragon Antirrhinum majus. For example, when there is a loss of B gene function, mutant flowers are produced with sepals in the first whorl as usual, but also in the second whorl instead of the normal petal formation. In the third whorl the lack of B function but presence of C function mimics the fourth whorl, leading to the formation of carpels also in the third whorl. Function The principal purpose of a flower is the reproduction of the individual and the species. All flowering plants are heterosporous, that is, every individual plant produces two types of spores. Microspores are produced by meiosis inside anthers and megaspores are produced inside ovules that are within an ovary. Anthers typically consist of four microsporangia and an ovule is an integumented megasporangium. Both types of spores develop into gametophytes inside sporangia. As with all heterosporous plants, the gametophytes also develop inside the spores, i.e. they are endosporic. In the majority of plant species, individual flowers have both functional carpels and stamens. Botanists describe these flowers as perfect or bisexual. and the species as hermaphroditic. In a minority of plant species, their flowers lack one or the other reproductive organ and are described as imperfect or unisexual. If the individual plants of a species each have unisexual flowers of both sexes then the species is monoecious. Alternatively, if each

x̄ - > Woodworking

    Woodworking is the skill of making items from wood and includes cabinet making, wood carving, joinery, carpentry, and woodturning. History Along with stone, clay, and animal parts, wood was one of the first materials worked by early humans. Microwear analysis of the Mousterian stone tools used by the Neanderthals shows that many were used to work wood. The development of civilization was closely tied to the development of increasingly greater degrees of skill in working with these materials. Among early finds of wooden tools are the worked sticks from Kalambo Falls. Clacton-on-Sea and Lehringen. 

    The spears from Schöningen provide some of the first examples of wooden hunting gear. Flint tools were used for carving. Since Neolithic times, carved wooden vessels are known for example, from the Linear Pottery culture wells at Kückhofen and Eythra. Examples of Bronze Age wood-carving include tree trunks worked into coffins from northern Germany and Denmark and wooden folding chairs. The site of Fellbach-Schmieden in Germany has provided fine examples of wooden animal statues from the Iron Age. Wooden idols from the La Tène period are known from a sanctuary at the source of the Seine in France. 

    Ancient Egypt There is significant evidence of advanced woodworking in ancient Egypt. Woodworking is depicted in many extant ancient Egyptian drawings, and a considerable amount of ancient Egyptian furniture has been preserved. Tombs represent a large collection of these artifacts and the inner coffins found in the tombs were also made of wood. The metal used by the Egyptians for woodworking tools was originally copper and eventually, after 2000 BC bronze as ironworking was unknown until much later. Commonly used woodworking tools included axes, adzes, chisels, pull saws, and bow drills. 

    Mortise and tenon joints are attested from the earliest Predynastic period. These joints were strengthened using pegs, dowels, and leather or cord lashings. Animal glue came to be used only in the New Kingdom period. Ancient Egyptians invented the art of veneering and used varnishes for finishing though the composition of these varnishes is unknown. Although different native acacias were used, as was the wood from the local sycamore and tamarisk trees, deforestation in the Nile valley resulted in the need for the importation of wood, notably cedar, but also Aleppo pine, boxwood, and oak, starting from the Second Dynasty. Ancient Rome Woodworking was essential to the Romans. It provided material for buildings, transportation, tools, and household items. 

    Wood also provided pipes, dye, waterproofing materials, and energy for heat. Although most examples of Roman woodworking have been lost. Pliny, while not a botanist, dedicated six books of his Natural History to trees and woody plants, providing a wealth of information on trees and their uses. Ancient China The progenitors of Chinese woodworking are considered to be Lu Ban and his wife Lady Yun from the Spring and Autumn period. Lu Ban is said to have introduced the plane, chalk-line, and other tools to China. 

    His teachings were supposedly left behind in the book Lu Ban Jing. Despite this, it is believed that the text was written some 1500 years after his death. This book is filled largely with descriptions of dimensions for use in building various items such as flower pots, tables, altars, etc., and also contains extensive instructions concerning Feng Shui. It mentions almost nothing of the intricate glue-less and nail-less joinery for which Chinese furniture was so famous. Modern-day With the advances in modern technology and the demands of industry, woodwork as a field has changed. 

    The development of Computer Numeric Controlled Machines, for example, has made us able to mass-produce and reproduce products faster, with less waste, and often more complex in design than ever before. CNC wood routers can carve complicated and highly detailed shapes into flat stock, to create signs or art. Rechargeable power tools speed up the creation of many projects and require much less body strength than in the past, for example when boring multiple holes. Skilled fine woodworking, however, remains a craft pursued by many. There remains demand for hand-crafted work such as furniture and arts, however, with the rate and cost of production, the cost for consumers is much higher. 

    Materials Historically, woodworkers relied upon the woods native to their region, until transportation and trade innovations made more exotic woods available to the craftsman Woods are typically sorted into three basic types: hardwoods typified by tight grain and derived from broadleaf trees, softwoods from coniferous trees, and man-made materials such as plywood and MDF. Hardwoods, botanically known as angiosperms, are deciduous and shed their leaves annually with temperature changes. Softwoods come from trees botanically known as gymnosperms, which are coniferous, cone-bearing, and stay green year-round. Softwood is most commonly found in the regions of the world with lower temperatures and is typically less durable, lighter in weight, and more vulnerable to pests and fungal attacks in comparison to hardwoods. They typically have a paler color and a more open grain than hardwoods, which contributes to the tendency of felled softwood to shrink and swell as it dries. 

    Hardwoods have a wide variety of properties, making it easy to find a hardwood to suit nearly any purpose, but they are especially suitable for outdoor use due to their strength and resilience to rot and decay. Within the USA fir, also known as Douglas fir, is inexpensive and common at local home centers. It has a characteristic straight, pronounced grain with a red-brown tint. However, its grain pattern is relatively plain and it does not stain well, so fir is commonly used when the finished product will be painted. While commonly used for building, this softwood would also be suitable for furniture-making. 

    Common hardwoods used for furniture Ash This hardwood is relatively easy to work with and takes stain well, but its white to light brown color with a straight grain is visually appealing on its own. However, ash is much more difficult to find than other common woods, and will not be found at the local home center. Larger lumber yards should have it in stock. Mahogany A hardwood, mahogany has a trademark reddish-brown to deep-red tint and is known as one of the great furniture woods". However, mahogany is not typically grown in sustainable forests, and thus runs a steep price at local lumberyards. 

    Because it has almost no grain and is notably soft Basswood is particularly popular with beginner carvers. It is used in many lower-cost instruments like guitars and electric basses. A vise is a form of the clamp, temporarily or permanently mounted as required. A woodworking vise is a vise specialized to the needs of a woodworker; numerous types have evolved Chisels are tools with a long blade, a cutting edge, and a handle. Used for cutting and shaping wood or other materials than the jigsaw or more delicate scroll saw, also regularly used in woodworking.