Flower Structure Flower Structure A Wild Strawberry Flower Flowers are the reproductive structures produced by plants which belong to the group known as Angiosperms, or 'Flowering Plants'. This group includes an enormous variety of different plants ranging from buttercups and orchids to oak trees and grasses. There are about 250,000 known species. A flower is basically made up of four concentric rings of structures. There is an outer ring of modified leaves called sepals. These provide protection to the flower before it opens and are usually green. This outer ring is known as the calyx. Inside the sepals is another ring of modified leaves called petals which are often brightly coloured. This layer is known as the corolla. Within the corolla are one or more stamens containing pollen, which are the male reproductive structures. In the very centre of the flower are the female reproductive organs. Female Reproductive Organ The female parts of a flower consist of an ovary, which contains one or more ovules, a style and the stigma. The ovary is at the base of the flower. From the ovary, extends a tubular structure called the style and on the top of the style is a surface receptive to pollen called the stigma.

The stigma can take many different forms, most of them designed to help trap pollen. There are many variations on this basic structural theme. Male Reproductive Organ The male parts of a flower consist of one or more stamens. Each stamen is made up of paired anthers (sacs containing pollen) on a filament or stalk. The anthers are the orange/yellow structures often seen in the centre of a flower. Pollen from the anthers of one flower is transferred to the stigma of another usually either by wind, or by animals, especially insects. Flowers do not always have the two outer layers of calyx and corolla. These two layers are most noticeable in plants which are pollinated by insects. The corolla, or petals are often brightly coloured with markings attractive to insects. The flowers may also be scented. For instance, Honeysuckle has showy, attractive flowers which attract insects by day. However, in the dark, their colourful show is not much use, and their heady scent then helps to attract night-flying moths. In insect-pollinated plants, there are also usually nectaries which secrete sugary nectar, located within the flower.

These provide an incentive to insects to visit the flowers. In the search for nectar, the insects will often get pollen grains caught on their bodies. This may then brush off onto the stigma of the next flower visited and in this way the flowers are pollinated. Many flowers have evolved very specific associations with a particular insect species or group of species. In these cases flower structure may be very specialized (e.g. orchids). Foxgloves (Digitalis purpurea) and Primroses (Primula vulgaris) show a range of adaptations to insect pollination. Wind pollination is also common in flowering plants. In this case, because there is no necessity to attract insects, the calyx and corolla of the flowers may be absent. This is a cross-section of a Foxglove (Digitalis purpurea) flower. It has been cut across the centre of the flower from top to bottom. The purple structures are the petals. The white circular markings on the petals act as guide lines, directing insects towards the nectaries hidden in the base of the flower. The green outer structures are the sepals.

The female reproductive structures are hidden, but the stamens with their yellow anthers are clearly visible at the top of the flower. Fertilization Once a pollen grain reaches the stigma of another flower of the same species, it will produce a pollen tube. This grows down through the style until it reaches an ovule. Fertilization then takes place, resulting in a seed. When pollen from one flower fertilizes the ovule of another flower, it is called cross pollination . If an ovule is fertilized by pollen from the same flower, it is called self fertilization. In evolutionary terms, this is generally not particularly favourable, as it leads to inbreeding. Most species therefore tend to be cross pollinated. In this case they need something to transfer the pollen from one flower to another. This might be insects, birds, wind or water. This need to use an outside agent to transfer the pollen has led to the extraordinary variety of shapes, colours, scents and arrangements of flowers seen today. corolla | plant anatomy | Britannica.com plant anatomy THIS IS A DIRECTORY PAGE. Britannica does not currently have an article on this topic. Figure 13: Representative forms of the corolla.

Encyclopædia Britannica, Inc. Costa’s hummingbird (Calypte costae) foraging for nectar in the bright red tubular flowers of ocotillo (Fouquieria splendens). Pollen is displaced onto the beak and head of the bird as it inserts its long tongue into the corolla tube where the nectar is located. © Robert A. Tyrrell/Oxford Scientific Films The petals of the delicate flower of Campsis radicans (trumpet creeper, or trumpet vine) form a corolla tube with five spreading lobes. A shortened calyx tube covers the base of the flower. © Robert and Linda Mitchell Zygomorphy, or bilateral symmetry, of the viola (Viola), which produces a delicate five-petaled flower with two dissimilar pairs. Nectar guides are prominent on the lower spurred petal. (Top) © G.A. Maclean—Oxford Scientific Films (Bottom) E.S. Ross Learn about this topic in these articles: in plant reproductive system: Angiosperms ...sepals (often greenish and leaflike), petals (often white or coloured other than green), stamens, and a pistil (or pistils).

The sepals are collectively known as the calyx, and the petals as the corolla; the calyx and corolla compose the perianth. If sepals or petals are lacking, the flower is said to be incomplete. Although incomplete, a flower that has both stamens and a pistil is said to... in angiosperm: The corolla The petals composing the corolla are typically brightly coloured or white and attract insects and birds for pollination (see below Reproduction: Pollination). The number of petals is usually the same as the number of sepals. Floral symmetry is defined by the petals (Figure 13). When the petals of the corolla are of the same size and shape and when they are equidistant from each other, the... in Asterales: Asteraceae ...involucre of small modified leaves (bracts). Furthermore, in more than half the members of the family, the flowers in the outermost row or rows of the head have a modified, mainly flat and elongate corolla that resembles an individual petal of most other flowers. Thus, the “petals” of a daisy or sunflower are actually the outermost flowers of the head.

An inflorescence of this... in Asterales: Campanulaceae Familiar Lobelia species include L. cardinalis (cardinal flower), which displays a brilliant red corolla, in contrast to the blue or white colours of the majority of related species. L. inflata (Indian tobacco) is native to eastern and central North America and has a tobacco taste; it was used as an emetic by Amerindians. This and other Lobelia species yield an... in Asterales: Other families ...pantropical beach plants along tropical seashores. The family has alternate (spiral) leaves, strongly bilaterally symmetric flowers with a plunger pollination mechanism, and an inferior ovary. The corolla is often divided to the base on one side, and the petals have marginal wings that may make each look trilobed. Several herbaceous species of Scaevola are important ornamentals,... in Asterales: Other families ...open from the outside of the head inward. The flowers are small and regularly symmetric, with sepals that either are transformed into spines or else are thick-spongy.

The outer layer of the tubular corolla is photosynthetic, the stamens are free, and the ovary is inferior. As with Asteraceae, the family has plunger pollination mechanisms and the ovary has two carpels, with only one ovule... Corolla of a Flower: Structure, Function & Definition - Video & Lesson Transcript | Study.com Corolla of a Flower: Structure, Function & Definition Watch short & fun videos Start Your Free Trial Today An error occurred trying to load this video. Try refreshing the page, or contact customer support. You must create an account to continue watching Register for a free trial Are you a student or a teacher? I am a student Start Your Free Trial To Continue Watching As a member, you'll also get unlimited access to over lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed. Coming up next: Cotyledon: Definition & Function You're on a roll. Keep up the good work! Your next lesson will play in 10 seconds 0:01 What Is a Corolla?

0:54 Variation in Structure 2:06 Function of the Corolla 4:12 Lesson Summary Add to Add to Add to Want to watch this again later? Log in or sign up to add this lesson to a Custom Course. Custom Courses are courses that you create from Study.com lessons. Use them just like other courses to track progress, access quizzes and exams, and share content. Teachers Organize and share selected lessons with your class. Make planning easier by creating your own custom course. Students Create a new course from any lesson page or your dashboard. From any lesson page: Click "Add to" located below the video player and follow the prompts to name your course and save your lesson. From your dashboard: Click on the "Custom Courses" tab, then click "Create course". Next, go to any lesson page and begin adding lessons. Edit your Custom Course directly from your dashboard. Personalize: Name your Custom Course and add an optional description or learning objective. Organize: Create chapters to group lesson within your course. Remove and reorder chapters and lessons at any time. Share your Custom Course or assign lessons and chapters.

Teacher Edition: Share or assign lessons and chapters by clicking the "Teacher" tab on the lesson or chapter page you want to assign. Students' quiz scores and video views will be trackable in your "Teacher" tab. Premium Edition: You can share your Custom Course by copying and pasting the course URL. Only Study.com members will be able to access the entire course. Create an account to start this course today Try it free for 5 days! Lesson Transcript Instructor: Margaret Cunningham Margaret has taught many Biology and Environmental Science courses and has Master's degrees in Environmental Science and Education. This lesson will investigate the structure of the flower known as the corolla. The lesson will also explore the variation in this structure, and its function and importance in plant reproduction. What Is a Corolla? When you look at a flowering plant, what's the first thing you notice? Is it the stem, the leaves, or the flower? On most flowering plants, the most noticeable feature is the brightly-colored petals of the flower. The petals of flowers are often arranged in a circle around the center of the flower, and this collective unit of petals is referred to as the corolla.

In addition to the corolla, most flowers have three other circles of structures that make up a complete flower. On the outside of the corolla, most flowers have sepals, small leaf-like structures that enclose the petals before the flower opens. The first circle of structures on the inside of the corolla is made up of the male reproductive organs of the flower, including the many stamen. The circle at the center of the flower consists of the female reproductive organs, which are collectively referred to as the pistil. Variation in Structure of the Corolla As you have probably noticed when observing a garden, there is a wide variety in the colors and designs of flowers. The corolla of different species of plants can vary in color, size, and the number of petals. Many large flowers have fewer petals within the corolla, while smaller flowers may have greater numbers of petals. Flowers can be divided into two different types based on the symmetry of their corolla. Flowers that have identical petals arranged in a circle around the center of the flower are said to have radial symmetry and are called actinomorphic flowers. Radial symmetry is when a mirror image can be produced when a line is drawn in any direction across the center of the flower.

Flowering plants that are actinomorphic include sunflowers, lilies, and buttercups. The second type of symmetry used to describe the corolla of flowers is called bilateral symmetry. This is when only one line can be drawn to create a mirror image through the middle of the flower. Flowers that have bilateral symmetry are called zygomorphic flowers, and they often have petals of different shapes and sizes within the corolla of the flower. The most common example of flowers that are zygomorphic are orchids. Function of the Corolla Overall, the main function of the corolla is to assist in the reproductive process of the plant. The petals of the corolla are designed to aid in pollination and therefore increase the chance of successful reproduction of the flower. Some plants are pollinated when wind picks up their pollen and transfers it to another flower of the same species. For plants that use wind pollination, the corolla assists this process by having small petals. The small petals do not block the wind, and make it possible for wind to move over the anther (which makes the pollen grains), and transfer it to another flower. The color and texture of the petals of the corolla also play an important role in pollination.

Many plants that rely on animal pollinators have specific animal species that pollinate them. In order to attract certain animal species, the flowers have developed petals with colors specifically pleasing to those animals. × Flower description glossary Terms describing flower anatomy Classical angiosperm phylogeny is based mainly on flower anatomy, and in particular, the arrangement and form of the principle parts. The fruiting body is used as well, but its structure is often apparent in the flowers. More recently, genetic studies have been employed to determine the relationship of various botanical groups to each other. Many parts of the old classification system have proven more or less consistent with these studies, but there have also been a large number of changes, even to large and well studied groups. The changes to the classical system have been far more extensive than in the animal kingdom, where the classical, anatomy-based phylogeny has held up remarkably well. As a result, botanical nomenclature has been undergoing a bit of a revolution in the last two decades, and the process (as of 2009) is still ongoing. A community known as the Angiosperm Phylogeny Group or APG has provided some centrality to this process, but there are many areas where no consensus has been reached.

Botany has always been prone to what might be termed "vanity species" with some genera (e.g. hieracium, the hawkweeds) having thousands of specific scientific names. The recent trend has been to recognize certain species as highly variable; but history dies hard, especially for those who discovered and described the "species". A flower is the reproductive unit of an angiosperm plant. There is an enormous variety of flowers, but all have some characteristics in common. The definitive characteristic of the angiosperms is the enclosed ovary, which contains and protects the developing seeds. Floral reproduction is bisexual, and flowers have "male" and "female" parts. The "male" or pollen-bearing part is called the stamen , and is composed of the filament and the anther . The "female" or seed-bearing part is called the pistil , and is composed of the ovary , the stigma , and the style . A flower may have exclusively male parts, exclusively female parts, or commonly, both. When there are separate flower types, both may occur on the same plant; occasionally a plant may bear only male or female flowers.

Surrounding the reproductive parts is the perianth , a double envelope consisting of an outer portion, the calyx , which forms the sepals , and an inner portion, the corolla , which forms the familiar petals . There may also be leafy elements, termed bracts , surrounding a flower. Individual flowers are often organized into a larger group or cluster, termed an inflorescence . The stalk supporting a single flower is called a pedicel , that supporting an inflorescence, or an isolated flower, a peduncle . Terms describing the inflorescence Inflorescence refers to the flowering body of a plant. These occur in an amazing variety of forms, from solitary flowers to enormously complex clusters, and there is an equally amazing variety of technical terminology used to describe them. Unfortunately, as with some other aspects of botany, this terminology is not universally standardized; different authors use different terms for the same structure, and sometimes the same terms in slightly or significantly different ways, and classify structures using different paradigms. We only brush the surface here, making use of a few of the most commonly used terms.

A basic and useful but somewhat non-immediately-obvious technical distinction is between determinate and indeterminate inflorescences. A determinate form has a fixed endpoint, usually a terminal flower that generally opens first. Lower side branches bear buds that open later. Indeterminate forms are often termed cymose or cymes. An indeterminate form is a shoot that can, at least theoretically, continue growing from the tip and producing more flowers indefinitely. The lower flowers open first, while upper buds may still be tiny and developing. Of course the whole process eventually comes to an end, but the distinction is frequently obvious. Indeterminate forms are termed racemose or racemes, though the latter term also has the more specific technical meaning described below. Of course in botany, nothing is ever simple. There are compound inflorescences that are mixtures of forms in every conceivable combination. Flower | Article about flower by The Free Dictionary Flower | Article about flower by The Free Dictionary Also found in: Dictionary , Thesaurus , Medical , Legal , Idioms , Wikipedia . flower, name for the specialized part of a plant containing the reproductive organs, applied to angiosperms only.

A flower may be thought of as a modified, short, compact branch bearing lateral appendages. Like twigs, flowers develop from buds, and the basic floral parts (sepal, petal, stamen, and carpel) are in actual fact greatly modified leaves. A typical flower is a concentric arrangement of these parts attached at their base to the receptacle, the tip of the stem. Outermost is a whorl of leaflike green sepals (the calyx) encircling a whorl of usually showy, colored petals (the corolla). Within the corolla the stamens, bearing anther sacs full of pollen pollen, minute grains, usually yellow in color but occasionally white, brown, red, or purple, borne in the anther sac at the tip of the slender filament of the stamen of a flowering plant or in the male cone of a conifer. ..... Click the link for more information. , surround the central carpels (ovary).

Inside the ovary at the base of the pistil are the ovules, containing the female sex cells; after fertilization of the egg, the ovule becomes the seed seed, fertilized and ripened ovule, consisting of the plant embryo, varying amounts of stored food material, and a protective outer seed coat. Seeds are frequently confused with the fruit enclosing them in flowering plants, especially in grains and nuts. ..... Click the link for more information. and the ovary becomes the fruit fruit, matured ovary of the pistil of a flower, containing the seed. After the egg nucleus, or ovum, has been fertilized (see fertilization) and the embryo plantlet begins to form, the surrounding ovule (see pistil) develops into a seed and the ovary wall (pericarp) around the ..... Click the link for more information. . The ovary and stamens are termed essential flower parts, the petals and sepals accessory parts. The number and arrangement of the floral organs vary considerably among the many families and orders of plants and are used in the classification of plants; they also indicate the degree of evolution of the plant.

In general, the higher a plant is on the evolutionary scale, the greater is the flower's complexity. The basic number of parts differs from class to class and from family to family; in monocotyledonous plants the parts generally occur in groups of three or in multiples of three, and in dicotyledons more often in groups of two, four, and five. Flowers may be staminate (lack carpels), carpellate, or both; staminate and carpellate flowers may appear on the same plant, on separate plants, or in the same inflorescence. One type of inflorescence, characteristic of the parsley family, is the umbel, in which the tiny florets are borne on separate stalks radiating out from the stem tip. Sometimes the parts serve unusual purposes: the true flowers of the dogwood and the poinsettia are inconspicuous, and the showy "petals" are really modified leaves called bracts. In the jack-in-the-pulpit the florets are clustered on a spike canopied by a large bract, the spathe; the hood of the lady's-slipper, on the other hand, is a modified sterile stamen.

Grass inflorescences are tiny spikelets sheathed by protective scales called glumes (the chaff or grain). Flowers have been cultivated and bred for their beauty and their perfume from earliest times and have accumulated a vast and intricate treasury of symbolic associations derived from legend and folklore. Individual flowers have been celebrated in heraldry ( rose rose, common name for some members of the Rosaceae, a large family of herbs, shrubs, and trees distributed over most of the earth, and for plants of the genus Rosa, the true roses. ..... Click the link for more information. ), in religion (lotus), and in politics ( violet violet, common name for some members of the Violaceae, a family of chiefly perennial herbs (and sometimes shrubs, small trees, or climbers) found on all continents. Violets, including the genus Viola ..... Click the link for more information. ) and have become emblems for many countries, including Switzerland (edelweiss), France (fleur-de-lis), Scotland (thistle), the Netherlands (tulip), and the United States (see state flowers state flowers.

Each state of the United States has designated, usually by legislative action, one flower as its floral emblem; the rose has been designated by Congress as the national flower of the United States. ..... Click the link for more information. ). Bibliography See S. Buchmann, The Reason for Flowers (2015). Flower A higher plant's sexual apparatus in the aggregate, including the parts that produce sex cells and closely associated attractive and protective parts (Fig. 1). “Flower” as used in this article will be limited, as is usual, to the angiosperms, plants with enclosed seeds and the unique reproductive process called double fertilization. In its most familiar form a flower is made up of four kinds of units arranged concentrically. The green sepals (collectively termed the calyx) are outermost, showy petals (the corolla) next, then the pollen-bearing units (stamens, androecium), and finally the centrally placed seed-bearing units (carpels, gynoecium). This is the “complete” flower of early botanists, but it is only one of an almost overwhelming array of floral forms.

One or more kinds of units may be lacking or hard to recognize depending on the species, and evolutionary modification has been so great in some groups of angiosperms that a flower cluster (inflorescence) can took like a single flower. Flower structure, median longitudinal section Flora diversity Most botanical terms are descriptive, and a botanist must have a large store of them to impart the multiformity of flowers. The examples that follow are only a smattering. An extra series of appendages alternating with the sepals, as in purple loosestrife, is an epicalyx. A petal with a broad distal region and a narrow proximal region is said to have a blade and claw: the crape myrtle has such petals. The term perianth, which embraces calyx and corolla and avoids the need to distinguish between them, is especially useful for a flower like the tulip, where the perianth parts are in two series but are alike in size, shape, and color. The members of such an undifferentiated perianth are tepals.

When the perianth has only one series of parts, however, they are customarily called sepals even if they are petallike, as in the windflower. A stamen commonly consists of a slender filament topped by a four-lobed anther, each lobe housing a pollen sac. In some plants one or more of the androecial parts are sterile rudiments called staminodes: a foxglove flower has four fertile stamens and a staminode. Carpellode is the corresponding term for an imperfectly formed gynoecial unit. A gynoecium is apocarpous if the carpels are separate (magnolia, blackberry) and syncarpous if they are connate (tulip, poppy). Or the gynoecium may regularly consist of only one carpel (bean, cherry). A solitary carpel or a syncarpous gynoecium can often be divided into three regions: a terminal, pollen-receptive stigma; a swollen basal ovary enclosing the undeveloped seeds (ovules); and a constricted, elongate style between the two.

The gynoecium can be apocarpous above and syncarpous below; that is, there can be separate styles and stigmas on one ovary (wood sorrel). Placentation: (a) parietal, (b) axile, and (c) free central Every flower cited so far has a superior ovary: perianth and androecium diverge beneath it (hypogyny). If perianth and androecium diverge from the ovary's summit, the ovary is inferior and the flower is epigynous (apple, banana, pumpkin). A flower is perigynous if the ovary is superior within a cup and the other floral parts diverge from the cup's rim (cherry). A syncarpous ovary is unilocular if it has only one seed chamber, plurilocular if septa divide it into more than one. The ovules of a plurilocular ovary are usually attached to the angles where the septa meet; this is axile placentation, a placenta being a region of ovular attachment.

There are other ways in which the ovules can be attached—apically, basally, parietally, or on a free-standing central placenta—each characteristic of certain plant groups (Fig. 2). The term bract can be applied to any leaflike part associated with one or more flowers but not part of a flower. Floral bracts are frequently small, even scalelike, but the flowering dogwood has four big petallike bracts below each flower cluster. The broad end of a flower stalk where the floral parts are attached is the receptacle. The same term is used, rather inconsistently, for the broad base bearing the many individual flowers (florets) that make up a composite flower like a dandelion or a sunflower. Sexuality A plant species is diclinous if its stamens and carpels are in separate flowers. A diclinous species is monoecious if each plant bears staminate and carpellate (pistillate) flowers, dioecious if the staminate and carpellate flowers are on different plants.

The corn plant, with staminate inflorescences (tassels) on top and carpellate inflorescences (ears) along the stalk, is monoecious. Hemp is a well-known dioecious plant. Nectaries Flowers pollinated by insects or other animals commonly have one or more nectaries, regions that secrete a sugar solution. A nectary can be nothing more than a layer of tissue lining part of a floral tube or cup (cherry), or it can be as conspicuous as the secretory spur of a nasturtium or a larkspur. It can be a cushionlike outgrowth at the base of a superior ovary (orange blossom) or atop an inferior ovary (parsley family). Gladiolus and a number of other monocotyledons have septal nectaries, deep secretory crevices where the carpels come together. Substances that give off floral odors—essential oils for the most part—ordinarily originate close to the nectar-producing region but are not coincident with it.

Production by the epidermis of perianth parts is most common, but in some species the odor emanates from a more restricted region and may even come from a special flap or brush. Most insect-pollinated plants have visual cues, some of them outside the human spectral range, as well as odor to bring the pollinators to the flowers and guide them to the nectar. See Secretory structures (plant) Inflorescence Inflorescence structure, the way the flowers are clustered or arranged on a flowering branch, is almost as diverse as floral structure. To appreciate this, one need only contrast the drooping inflorescences (catkins) of a birch tree with the coiled flowers of a forget-me-not or with the solitary flower of a tulip. In some cases one kind of inflorescence characterizes a whole plant family. Queen Anne's lace and other members of the parsley family (Umbelliferae) have umbrellalike inflorescences with the flower stalks radiating from almost the same point in a cluster.

The stalkless flowers (florets) of the grass family are grouped into clusters called spikelets, and these in turn are variously arranged in different grasses. Flowers of the arum family (calla lily, jack-in-the-pulpit), also stalkless, are crowded on a thick, fleshy, elongate axis. In the composite family, florets are joined in a tight head at the end of the axis; the heads of some composites contain two kinds, centrally placed florets with small tubular corollas and peripheral ray florets with showy, strap-shaped corollas (the “petals” one plucks from a daisy). See Inflorescence Anatomy Some of the general anatomical features of leaves can be found in the floral appendages. A cuticle-covered epidermis overlies a core of parenchyma cells in which there are branching vascular bundles (solitary bundles in most stamens). Sepal parenchyma and petal parenchyma are often spongy, but palisade parenchyma occurs only rarely in flowers and then only in sepals.

As in other parts of the plant, color comes mostly from plastids in the cytoplasm and from flavonoids in the cell sap. Cells of the petal epidermis may have folded side walls that interlock so as to strengthen the tissue. In some species the outer walls of the epidermis are raised as papillae; apparently, this is part of the means of attracting pollinators, for the papillae are light reflectors. Stamen As a stamen develops, periclinal divisions in the second cell layer of each of its four lobes start a sequence that will end with the shedding of pollen. The first division makes two cell layers. The outer daughter cells give rise to the wall of the pollen sac, and the inner ones are destined to become pollen after further divisions. When mature, a pollen sac typically has a prominent cell layer just below a less distinctive epidermis. The inner wall and the side walls of an endothecium cell carry marked thickenings, but the outer wall does not. Splitting of the ripe anther is due partly to the way in which these differentially thickened walls react to drying and shrinking and partly to the smaller size of the cells along the line of splitting.

See Pollen Carpel Like other floral parts, a carpel is made up of epidermis, parenchyma, and vascular tissue. In addition, a carpel commonly has a special tissue system on which pollen germinates and through which, or along which, pollen tubes are transmitted to the ovules. Most angiosperms have solid styles, and the transmitting tissue is a column of elongate cells whose softened walls are the medium for tubal growth. The epidermis at the stigmatic end of a carpel usually changes to a dense covering of papillae or hairs; the hairs can be unicellular or pluricellular, branched or unbranched. In taxa with hollow styles, the transmitting tissue is a modified epidermis running down the stylar canal. There are two kinds of receptive surfaces, and they are distributed among the monocotyledons and the dicotyledons with taxonomic regularity. One kind has a fluid medium for germinating the pollen, and the other has a dry proteinaceous layer over the cuticle. The proteins of the dry stigmas have a role in the incompatibility reactions that encourage outbreeding.

Ovule Ovule development usually takes place as the gynoecium forms, but it may be retarded when there is a long interval between pollination and fertilization (oaks, orchids). A typical ovule has a stalk (funiculus), a central bulbous body (nucellus), and one or two integuments (precursors of seed coats), which cover the nucellus except for a terminal pore (micropyle). Orientation of the ovule varies from group to group. It can be erect on its stalk or bent one way or another to differing degrees. There are also taxonomic differences in the extent to which the ovule is vascularized by branches from the gynoecial vascular system. See Fruit , Reproduction (plant) Flower a short, limited-in-growth reproductive shoot that performs the functions of microsporogenesis, megasporogenesis, pollination (effected by pollen carrier-agents), fertilization, embryonic development, and fruit formation. The flower is borne at the end of a main or lateral stem. The peduncle, the part of the stem that bears the flower, is usually leafless.

Often it is very short and barely visible; in this case the flower is said to be sessile, or attached. The peduncle becomes the short axis of the flower, which is called the flower receptacle, or torus. The variously shaped receptacle is usually broader than the peduncle and is characterized by barely noticeable internodes. Its nodes bear all the various parts of the flower: the sterile sepals and petals and the fertile stamens and carpels. The sepals, which together form the calyx, usually serve as protective organs of the flower, especially before blooming; they often also function as supplementary organs of photosynthesis. The sepals often become petallike, taking on the functions of petals (for example, in Clematis). In some instances, through the process of evolution, the sepals have concresced into a synsepalous calyx. The petals, which serve to attract pollinators, are collectively known as the corolla. The calyx and the corolla together make up the perianth. When the flower has both a calyx and a corolla, the perianth is said to be double.

A simple perianth is one in which the petals are absent or in which there are no marked differences between the calyx and the corolla. In the center of the flower are located the stamens and carpels. The stamens are microsporophylls both in function and in origin. The most primitive ones, as seen in a number of representatives of the families Magnoliaceae and Winteraceae, consist of a broad ribbonlike membrane equipped with four linear microsporangia that are approximate in pairs and that are more or less embedded in the tissue of the membrane. In the course of evolution the stamens gradually became differentiated into the filament and the anther, which consists of two halves joined by a continuation of the filament. The stamens are known collectively as the androecium. The filaments often concresce together or with elements of the perianth or carpels. Sometimes the stamens concresce together by both the filaments and anthers or by the anthers only. The carpels consist of highly modified and specialized megasporophylls.

A single carpel is often called a simple pistil (the term “pistil” is used in various senses, often creating confusion). The most primitive type of carpel is retained in the genera Degeneria (family Degeneriaceae) and Tasmania (family Winteraceae). It consists of a short stalk and a relatively thin adaxially folded (conduplicate) membrane; externally it strongly resembles the conduplicate leaves folded into the bud. Along the carpel pass three conducting bundles (veins), of which the middle or dorsal one branches profusely. Between the middle and lateral veins are numerous ovules. In the early stages of development the margins of the carpels of Degeneria almost do not touch each other; protection of the ovules during flowering is ensured by the proximity of the broad lateral parts of the carpel, which are located between the carpel’s margins and placentas. These approximate internal surfaces concresce only after flowering, that is, during fruit development. The most diverse stages of concrescence are observed in other representatives of Winteraceae. In all flowering plants the carpel has a special glandular tissue, called the stigma, that serves to capture pollen.

In Degeneria and Tasmania the stigma is primitive and extends the entire length of the carpel. The upper part of the carpel usually extends into a slender, sterile columnar process, which supports the stigma above the ovary—the fertile part of the carpel—and serves as a passageway to the pollen tube. This specialized process is called the style or the stylodium (in which case the term “style” is only used in reference to concresced stylodia). In the early stages of evolution, the style is characterized by a descending stigma; in later stages the stigma gradually becomes localized at the top. The aggregate of carpels in the flower is called the gynoecium. The most primitive types of gynoecia with free carpels are called apocarpous; such gynoecia characterize Magnolia, Ranunculus, and Paeonia. In the process of evolution the carpels gradually concresced among themselves, and from the apocarpous gynoecium there emerged the coenocarpous gynoecium, in which the stylodia are free, or concresced to form the style.

The evolution of both the coenocarpous and apocarpous gynoecia was usually accompanied by a decrease in the number of carpels and, in most cases, in the number of ovules. An extreme form is the pseudomonomerous gynoecium, in which a single carpel is fertile and completely developed (as seen in elm, mulberry, nettle, and hemp). Most flowers have nectaries—special excretory organs for the production of nectar. Nectaries originated in the most diverse forms in the evolution of flowering plants and on the most diverse morphological bases, that is, on the most diverse parts of the flower. Primitive types of flowers are characterized by a relatively long receptacle, but in some cases, for example, in Myosurus and some Magnolia, there is a greatly elongated receptacle of secondary origin. In the process of evolution there has been a gradual shortening of the receptacle, as a result of which the flower parts have grown closer together and the initial spiral formation has changed to a cyclic one. The parts of a cyclic flower are usually arranged in whorls; less commonly, they are opposite.

Cyclic flowers are found more frequently than spiral ones. In an intermediate position are spirocyclic flowers, such as those of Ranunculus. Primitive flowers are actinomorphic (regular); that is, they can be divided by a vertical plane passing through the symmetrical axis into equal halves in no less than two directions. Owing to the biology of pollination, actinomorphic flowers gave rise to zygomorphic (irregular) ones, which can be divided into two halves only in a single direction (for example, the blossom of the sweet pea or snapdragon). In contrast to actinomorphic and zygomorphic flowers, which are both symmetrical, there are also asymmetrical flowers, which cannot be divided into two equal halves by a plane of symmetry (for example, cannas). Flowers may be bisexual or unisexual. Unisexual flowers originated from bisexual ones as a result of the reduction of the stamens in some cases and of the carpels in others. Unisexual flowers often retain the rudiments of stamens and carpels. It is conjectured that the flower is descended from the reproductive shoots of the supposed ancestors of flowering plants—seed ferns.

As a result of shortening, the shoot axis was converted into a receptacle. Simplification of the segmented microsporophylls and megasporophylls resulted in the simple unbranched stamens and carpels of flowering plants. (The hypothesis that the flower is descended from the strobile of Cycadaceae, Gnetaceae, or Bennettitaceae is improbable.) The evolution of the flower, like the evolution of the strobiles of various groups of gymnosperms, set off in various directions. Thus, current theories are based on the proposition that the fundamental parts of the flower—the stamens and carpels—are descended from the sporebearing organs of the ancestors of flowering plants. It is difficult to say with certainty whether these primitive spore cases were somewhat rounded or flat or whether they were achlorophyllous or green. It is most probable that they consisted of flat and more or less simplified, possibly lobular, sporophylls, which, especially if they were megasporophylls, probably partially performed the function of photosynthesis. REFERENCES Flowers (dreams) When we look at flowers, most of us feel some joy and vitality.

At the very least, we appreciate their beauty and see their value. Flowers are beautiful and in our dreams they could represent the simplest feelings of contentment or the deepest feelings of spiritual completeness. A circular flower is a friendly sign that could be the “mandala” symbol or the symbol of wholeness that represents the “psychic center of the personality.” Additionally, the colors could symbolize the psychic centers in our bodies called chakras. Flowers also represent hope and positive growth, along with simplicity, innocence, and possibly virginity. Parts of the Flower Corolla | Garden Guides Parts of the Flower Corolla Parts of the Flower Corolla Reason for flagging? Submit The corolla is a term that means all the petals of the flower. However, in order to understand what the corolla is, you need to understand that what looks like a petal is not always a petal. In fact, some flowers don't even have petals. This might seem confusing, but once you understand a little more about basic flower structure, it is easy to understand what parts of the flower make up the corolla. Petals Petals are soft, thin, typically brightly colored, modified leaves.

Petals form whorls around the reproductive organs of a flower. The petals are usually the second whorl and have sepals surrounding them. However, not all plants have petals. Some, such as hellebores, have petaloid sepals, which means that the sepals are modified to look like petals. Corolla As said earlier, all the petals of the flower make up the corolla. In the picture of the rose, the corolla includes all of the pink petals, but does not include the green sepals (described below) nor does it include the reproductive parts of the flower such as the stamen and pistol. Sepals The sepals are part of the outer whorl of the flower. They are usually green, but not always. For example, day lilies have colored sepals. Like the corolla, they are non-fertile parts of the flower. Although they are not part of the corolla, the corolla and the sepals of the flower are known as the perianth. Calyx The calyx includes all the sepals of the flower. It is the protective cover of the flower that once enclosed the bud.

Tepals Tepals is a term traditionally used when flowers do not have distinguishable sepals and petals. A good example of this is the tulip, where both the inner and outer whorls appear the same. Perianth The perianth is the outer part of the flower and includes both the calyx and the corolla of the flower. Basically, the term is used to refer to all the non-fertile parts of the flower. This term is often used when the calyx (sepals) and corolla (petals) are hard to distinguish from each other. Who Can Help

Question: What is the corolla of a flower commonly known as?
Answer: Petals