Flowering plant
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
Wood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material, a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves, it conveys water and nutrients between the leaves, other growing tissues, the roots. Wood may refer to other plant materials with comparable properties, to material engineered from wood, or wood chips or fiber. Wood has been used for thousands of years for fuel, as a construction material, for making tools and weapons and paper. More it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate.
As of 2005, the growing stock of forests worldwide was about 434 billion cubic meters, 47% of, commercial. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991 3.5 billion cubic meters of wood were harvested. Dominant uses were for building construction. A 2011 discovery in the Canadian province of New Brunswick yielded the earliest known plants to have grown wood 395 to 400 million years ago. Wood can be dated by carbon dating and in some species by dendrochronology to determine when a wooden object was created. People have used wood for thousands of years for many purposes, including as a fuel or as a construction material for making houses, weapons, packaging and paper. Known constructions using wood date back ten thousand years. Buildings like the European Neolithic long house were made of wood. Recent use of wood has been enhanced by the addition of bronze into construction; the year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at the time a tree was cut.
Wood, in the strict sense, is yielded by trees, which increase in diameter by the formation, between the existing wood and the inner bark, of new woody layers which envelop the entire stem, living branches, roots. This process is known as secondary growth; these cells go on to form thickened secondary cell walls, composed of cellulose and lignin. Where the differences between the four seasons are distinct, e.g. New Zealand, growth can occur in a discrete annual or seasonal pattern, leading to growth rings. If the distinctiveness between seasons is annual, these growth rings are referred to as annual rings. Where there is little seasonal difference growth rings are to be indistinct or absent. If the bark of the tree has been removed in a particular area, the rings will be deformed as the plant overgrows the scar. If there are differences within a growth ring the part of a growth ring nearest the center of the tree, formed early in the growing season when growth is rapid, is composed of wider elements.
It is lighter in color than that near the outer portion of the ring, is known as earlywood or springwood. The outer portion formed in the season is known as the latewood or summerwood. However, there are major differences, depending on the kind of wood; as a tree grows, lower branches die, their bases may become overgrown and enclosed by subsequent layers of trunk wood, forming a type of imperfection known as a knot. The dead branch may not be attached to the trunk wood except at its base, can drop out after the tree has been sawn into boards. Knots affect the technical properties of the wood reducing the local strength and increasing the tendency for splitting along the wood grain, but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a circular "solid" piece of wood around which the grain of the rest of the wood "flows". Within a knot, the direction of the wood is up to 90 degrees different from the grain direction of the regular wood. In the tree a knot is either the base of a dormant bud.
A knot is conical in shape with the inner tip at the point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud. In grading lumber and structural timber, knots are classified according to their form, size and the firmness with which they are held in place; this firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow. Knots materially affect cracking and warping, ease in working, cleavability of timber, they are defects which weaken timber and lower its value for structural purposes where strength is an important consideration. The weakening effect is much more serious when timber is subjected to forces perpendicular to the grain and/or tension than when under load along the grain and/or compression; the extent to which knots affect the strength of a beam depends upon their position, size and condition. A knot on the upper side is compressed. If there is a season check
Cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough and sometimes rigid, it provides the cell with both structural support and protection, acts as a filtering mechanism. Cell walls are present in most prokaryotes, in algae and fungi but in other eukaryotes including animals. A major function is to act as pressure vessels, preventing over-expansion of the cell when water enters; the composition of cell walls varies between species and may depend on cell type and developmental stage. The primary cell wall of land plants is composed of the polysaccharides cellulose and pectin. Other polymers such as lignin, suberin or cutin are anchored to or embedded in plant cell walls. Algae possess cell walls made of glycoproteins and polysaccharides such as carrageenan and agar that are absent from land plants. In bacteria, the cell wall is composed of peptidoglycan; the cell walls of archaea have various compositions, may be formed of glycoprotein S-layers, pseudopeptidoglycan, or polysaccharides.
Fungi possess cell walls made of the N-acetylglucosamine polymer chitin. Unusually, diatoms have a cell wall composed of biogenic silica. A plant cell wall was first observed and named by Robert Hooke in 1665. However, "the dead excrusion product of the living protoplast" was forgotten, for three centuries, being the subject of scientific interest as a resource for industrial processing or in relation to animal or human health. In 1804, Karl Rudolphi and J. H. F. Link proved. Before, it had been thought that fluid passed between them this way; the mode of formation of the cell wall was controversial in the 19th century. Hugo von Mohl advocated the idea. Carl Nägeli believed that the growth of the wall in thickness and in area was due to a process termed intussusception; each theory was improved in the following decades: the apposition theory by Eduard Strasburger, the intussusception theory by Julius Wiesner. In 1930, Ernst Münch coined the term apoplast in order to separate the "living" symplast from the "dead" plant region, the latter of which included the cell wall.
By the 1980s, some authors suggested replacing the term "cell wall" as it was used for plants, with the more precise term "extracellular matrix", as used for animal cells, but others preferred the older term. Cell walls serve similar purposes in those organisms, they may give cells offering protection against mechanical stress. In multicellular organisms, they permit the organism to hold a definite shape. Cell walls limit the entry of large molecules that may be toxic to the cell, they further permit the creation of stable osmotic environments by preventing osmotic lysis and helping to retain water. Their composition and form may change during the cell cycle and depend on growth conditions. In most cells, the cell wall is flexible, meaning that it will bend rather than holding a fixed shape, but has considerable tensile strength; the apparent rigidity of primary plant tissues is enabled by cell walls, but is not due to the walls' stiffness. Hydraulic turgor pressure creates this rigidity, along with the wall structure.
The flexibility of the cell walls is seen when plants wilt, so that the stems and leaves begin to droop, or in seaweeds that bend in water currents. As John Howland explains Think of the cell wall as a wicker basket in which a balloon has been inflated so that it exerts pressure from the inside; such a basket is rigid and resistant to mechanical damage. Thus does the prokaryote cell gain strength from a flexible plasma membrane pressing against a rigid cell wall; the apparent rigidity of the cell wall thus results from inflation of the cell contained within. This inflation is a result of the passive uptake of water. In plants, a secondary cell wall is a thicker additional layer of cellulose which increases wall rigidity. Additional layers may be formed by suberin in cork cell walls; these compounds are rigid and waterproof. Both wood and bark cells of trees have secondary walls. Other parts of plants such as the leaf stalk may acquire similar reinforcement to resist the strain of physical forces.
The primary cell wall of most plant cells is permeable to small molecules including small proteins, with size exclusion estimated to be 30-60 kDa. The pH is an important factor governing the transport of molecules through cell walls. Cell walls evolved independently including within the photosynthetic eukaryotes. In these lineages, the cell wall is related to the evolution of multicellularity, terrestrialization and vascularization; the walls of plant cells must have sufficient tensile strength to withstand internal osmotic pressures of several times atmospheric pressure that result from the difference in solute concentration between the cell interior and external solutions. Plant cell walls vary from 0.1 to several µm in thickness. Up to three strata or layers may be found in plant cell walls: The primary cell wall a thin and extensible layer formed while the cell is growing; the secondary cell wall, a thick layer formed inside the primary cell wall after the cell is grown. It is not found in all cell types.
Some cells, such as the conducting cells in xylem, possess a secondary wall containing lignin, which strengthens and waterproofs the wall. The middle lamella, a layer rich in pectins; this outermost layer
Bud
In botany, a bud is an undeveloped or embryonic shoot and occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be specialized to develop flowers or short shoots, or may have the potential for general shoot development; the term bud is used in zoology, where it refers to an outgrowth from the body which can develop into a new individual. The buds of many woody plants in temperate or cold climates, are protected by a covering of modified leaves called scales which enclose the more delicate parts of the bud. Many bud scales are covered by a gummy substance; when the bud develops, the scales may enlarge somewhat but just drop off, leaving a series of horizontally-elongated scars on the surface of the growing stem. By means of these scars one can determine the age of any young branch, since each year's growth ends in the formation of a bud, the formation of which produces an additional group of bud scale scars.
Continued growth of the branch causes these scars to be obliterated after a few years so that the total age of older branches cannot be determined by this means. In many plants scales do not form over the bud, the bud is called a naked bud; the minute underdeveloped leaves in such buds are excessively hairy. Naked buds are found in some shrubs, like some species of the Sumac and Viburnums and in herbaceous plants. In many of the latter, buds are more reduced consisting of undifferentiated masses of cells in the axils of leaves. A terminal bud occurs on the end of a stem and lateral buds are found on the side. A head of cabbage is an exceptionally large terminal bud, while Brussels sprouts are large lateral buds. Since buds are formed in the axils of leaves, their distribution on the stem is the same as that of leaves. There are alternate and whorled buds, as well as the terminal bud at the tip of the stem. In many plants buds appear in unexpected places: these are known as adventitious buds, it is possible to find a bud in a remarkable series of gradations of bud scales.
In the buckeye, for example, one may see a complete gradation from the small brown outer scale through larger scales which on unfolding become somewhat green to the inner scales of the bud, which are remarkably leaf-like. Such a series suggests that the scales of the bud are in truth leaves, modified to protect the more delicate parts of the plant during unfavorable periods. Buds are useful in the identification of plants for woody plants in winter when leaves have fallen. Buds may be classified and described according to different criteria: location, status and function. Botanists use the following terms: for location: terminal, when located at the tip of a stem; the term is usable as a synonym of resting, but is better employed for buds waiting undeveloped for years, for example epicormic buds. Buds The term bud is used by analogy within zoology as well, where it refers to an outgrowth from the body which develops into a new individual, it is a form of asexual reproduction limited to animals or plants of simple structure.
In this process a portion of the wall of the parent cell pushes out. The protuberance thus formed enlarges while at this time the nucleus of the parent cell divides. One of the resulting nuclei passes into the bud, the bud is cut off from its parent cell and the process is repeated; the daughter cell will begin to bud before it becomes separated from the parent, so that whole colonies of adhering cells may be formed. Cross walls cut off the bud from the original cell
Cataphyll
In plant morphology, a cataphyll is a reduced, small leaf. Many plants have both "true leaves" which perform the majority of photosynthesis, cataphylls that are modified to perform other specialized functions. Cataphylls include bracts and bud scales, as well as any small leaves that resemble scales, which are known as scale leaves; some cataphylls have a primary function other than photosynthesis. The functions of cataphylls such as bud scales may be short-lived and they are shed after the need for them is past. From the Greek Ancient Greek: κατά, Ancient Greek: φύλλον, leaf; some kinds of cataphylls perform a transient function, after which they may be shed. Those that are shed early are said to be caducous, but that term can apply to any organ, shed early, not only leaves; the sepals of Papaver species are shed during the opening of the petals, as such they are a dramatic example of caducous leaves. Many other forms of cataphylls, such as some spines, are persistent, but cannot perform their major function until they die, whether they physically get shed or not.
Examples of various kinds of cataphylls include bud-scales, bulb-scales, corm-scales, rhizome-scales, scaly bracts, spines. Each of these occurs in various contexts. Protective masses of dead leaves encircle the stems of some species of palm trees or aloes, but those are not regarded as cataphylls because their primary function while alive was photosynthesis, as is usual for true leaves. Cotyledons are regarded as a class of cataphyll, though many kinds of cotyledon function as living tissue and remain alive till the end of their function at least, at which time they wither and may drop off, they begin as leaf rudiments and many kinds accumulate nutrient materials for storage, starting to give up their stored material as the plant begins to germinate. Some, such as the cotyledons of many legumes and cucurbits develop chlorophyll and perform the first photosynthesis for the germinating plant, it is a matter of context and preference whether one regards any particular kind of spine as a cataphyll or not.
The terminology for glochids in particular is confusing, as they are variously and arbitrarily referred to as spines and more. Morphologically only spines could speaking be cataphylls, because the others are not leaves, but in the current context the point is hardly worth pursuing. Like bulb-scales, corm-scales are the basal parts of the photosynthetic leaves that show above ground; some species of cormous plants, such as some Lapeirousias produce cataphyllous leaves that act as nothing more than tunic leaves for the corm. Unlike bulb-scales however, the corm tunic has no significant storage function. Leaf shape Leaf size
Plant stem
A stem is one of two main structural axes of a vascular plant, the other being the root. The stem is divided into nodes and internodes: The nodes hold one or more leaves, as well as buds which can grow into branches. Adventitious roots may be produced from the nodes; the internodes distance one node from another. The term "shoots" is confused with "stems". In most plants stems are located above the soil surface but some plants have underground stems. Stems have four main functions which are: Support for and the elevation of leaves and fruits; the stems keep the leaves in the light and provide a place for the plant to keep its flowers and fruits. Transport of fluids between the roots and the shoots in the xylem and phloem Storage of nutrients Production of new living tissue; the normal lifespan of plant cells is one to three years. Stems have cells called meristems. Stems are specialized for storage, asexual reproduction, protection or photosynthesis, including the following: Acaulescent – used to describe stems in plants that appear to be stemless.
These stems are just short, the leaves appearing to rise directly out of the ground, e.g. some Viola species. Arborescent – tree like with woody stems with a single trunk. Axillary bud – a bud which grows at the point of attachment of an older leaf with the stem, it gives rise to a shoot. Branched – aerial stems are described as being branched or unbranched Bud – an embryonic shoot with immature stem tip. Bulb – a short vertical underground stem with fleshy storage leaves attached, e.g. onion, tulip. Bulbs function in reproduction by splitting to form new bulbs or producing small new bulbs termed bulblets. Bulbs are a combination of stem and leaves so may better be considered as leaves because the leaves make up the greater part. Caespitose – when stems grow in a tangled mass or clump or in low growing mats. Cladode – a flattened stem that appears more-or-less leaf like and is specialized for photosynthesis, e.g. cactus pads. Climbing -- stems that wrap around other plants or structures. Corm – a short enlarged underground, storage stem, e.g. taro, gladiolus.
Decumbent -- stems that lie flat on the turn upwards at the ends. Fruticose -- stems. Herbaceous – non woody, they die at the end of the growing season. Internode – an interval between two successive nodes, it possesses the ability to elongate, either from its base or from its extremity depending on the species. Node – a point of attachment of a leaf or a twig on the stem in seed plants. A node is a small growth zone. Pedicel – stems that serve as the stalk of an individual flower in an inflorescence or infrutescence. Peduncle – a stem that supports an inflorescence Prickle – a sharpened extension of the stem's outer layers, e.g. roses. Pseudostem – a false stem made of the rolled bases of leaves, which may be 2 or 3 m tall as in banana Rhizome – a horizontal underground stem that functions in reproduction but in storage, e.g. most ferns, iris Runner – a type of stolon, horizontally growing on top of the ground and rooting at the nodes, aids in reproduction. E.g. garden strawberry, Chlorophytum comosum.
Scape – a stem that holds flowers that comes out of the ground and has no normal leaves. Hosta, Iris, Garlic. Stolon – a horizontal stem that produces rooted plantlets at its nodes and ends, forming near the surface of the ground. Thorn – a modified stem with a sharpened point. Tuber – a swollen, underground storage stem adapted for storage and reproduction, e.g. potato. Woody – hard textured stems with secondary xylem. Stem consist of three tissues, dermal tissue, ground tissue and vascular tissue; the dermal tissue covers the outer surface of the stem and functions to waterproof and control gas exchange. The ground tissue consists of parenchyma cells and fills in around the vascular tissue, it sometimes functions in photosynthesis. Vascular tissue provides structural support. Most or all ground tissue may be lost in woody stems; the dermal tissue of aquatic plants stems. The arrangement of the vascular tissues varies among plant species. Dicot stems with primary growth have pith in the center, with vascular bundles forming a distinct ring visible when the stem is viewed in cross section.
The outside of the stem is covered with an epidermis, covered by a waterproof cuticle. The epidermis may contain stomata for gas exchange and multicellular stem hairs called trichomes. A cortex consisting of hypodermis and endodermis is present above the pericycle and vascular bundles. Woody dicots and many nonwoody dicots have secondary growth originating from their lateral or secondary meristems: the vascular cambium and the cork cambium or phellogen; the vascular cambium forms between the xylem and phloem in the vascular bundles and connects to form a continuous cylinder. The vascular cambium cells divide to produce secondary xylem to the inside and secondary phloem to the outside; as the stem increases in diameter due to production of secondary xylem and secondary phloem, the cortex and epidermis are destroyed. Before the cortex is destroyed, a cork cambium develops there; the cork cambium divides to produce waterproof cork cells externally and sometimes phelloderm cells internally. Those three tissues form the periderm.
Areas of loosely pack
History of botany
The history of botany examines the human effort to understand life on Earth by tracing the historical development of the discipline of botany—that part of natural science dealing with organisms traditionally treated as plants. Rudimentary botanical science began with empirically-based plant lore passed from generation to generation in the oral traditions of paleolithic hunter-gatherers; the first written records of plants were made in the Neolithic Revolution about 10,000 years ago as writing was developed in the settled agricultural communities where plants and animals were first domesticated. The first writings that show human curiosity about plants themselves, rather than the uses that could be made of them, appears in the teachings of Aristotle's student Theophrastus at the Lyceum in ancient Athens in about 350 BC. In Europe, this early botanical science was soon overshadowed by a medieval preoccupation with the medicinal properties of plants that lasted more than 1000 years. During this time, the medicinal works of classical antiquity were reproduced in manuscripts and books called herbals.
In China and the Arab world, the Greco-Roman work on medicinal plants was extended. In Europe the Renaissance of the 14th–17th centuries heralded a scientific revival during which botany emerged from natural history as an independent science, distinct from medicine and agriculture. Herbals were replaced by floras: books; the invention of the microscope stimulated the study of plant anatomy, the first designed experiments in plant physiology were performed. With the expansion of trade and exploration beyond Europe, the many new plants being discovered were subjected to an rigorous process of naming and classification. Progressively more sophisticated scientific technology has aided the development of contemporary botanical offshoots in the plant sciences, ranging from the applied fields of economic botany, to the detailed examination of the structure and function of plants and their interaction with the environment over many scales from the large-scale global significance of vegetation and plant communities through to the small scale of subjects like cell theory, molecular biology and plant biochemistry.
Botany and zoology are the core disciplines of biology whose history is associated with the natural sciences chemistry and geology. A distinction can be made between botanical science in a pure sense, as the study of plants themselves, botany as applied science, which studies the human use of plants. Early natural history divided pure botany into three main streams morphology-classification and physiology – that is, external form, internal structure, functional operation; the most obvious topics in applied botany are horticulture and agriculture although there are many others like weed science, plant pathology, pharmacognosy, economic botany and ethnobotany which lie outside modern courses in botany. Since the origin of botanical science there has been a progressive increase in the scope of the subject as technology has opened up new techniques and areas of study. Modern molecular systematics, for example, entails the principles and techniques of taxonomy, molecular biology, computer science and more.
Within botany there are a number of sub-disciplines that focus on particular plant groups, each with their own range of related studies. Included here are: phycology, pteridology and palaeobotany and their histories are treated elsewhere. To this list can be added mycology, the study of fungi, which were once treated as plants, but are now ranked as a unique kingdom. Nomadic hunter-gatherer societies passed on, by oral tradition, what they knew about the different kinds of plants that they used for food, poisons, for ceremonies and rituals etc; the uses of plants by these pre-literate societies influenced the way the plants were named and classified—their uses were embedded in folk-taxonomies, the way they were grouped according to use in everyday communication. The nomadic life-style was drastically changed when settled communities were established in about twelve centres around the world during the Neolithic Revolution which extended from about 10,000 to 2500 years ago depending on the region.
With these communities came the development of the technology and skills needed for the domestication of plants and animals and the emergence of the written word provided evidence for the passing of systematic knowledge and culture from one generation to the next. During the Neolithic Revolution plant knowledge increased most through the use of plants for food and medicine. All of today's staple foods were domesticated in prehistoric times as a gradual process of selection of higher-yielding varieties took place unknowingly, over hundreds to thousands of years. Legumes were cultivated on all continents but cereals made up most of the regular diet: rice in East Asia and barley in the Middle east, maize in Central and South America. By Greco-Roman times popular food plants of today, including grapes, apples and olives, were being listed as named varieties in early manuscripts. Botanical authority William Stearn has observed that "cultivated plants are mankind's most vital and precious heritage from remote antiquity".
It is from the Neolithic, in about 3000 BC, that we glimpse the first known illustrations of plants and read descript
