Botany lecture notes

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Botany Kenneth R. Robertson, Ph.D., Plant Systematist, Illinois Natural History Survey, and Affiliate, CHAPTER 4 Department of Plant Biology, University of Illinois at Urbana-Champaign Botany Stephen R. Downie, Ph.D., Professor of Plant Biology, University of Illinois The majority of the text for this chapter is adapted from lecture notes for at Urbana-Champaign a University of Illinois course, Systematics of Plants, taught by Kenneth R. Robertson and Stephen R. Downie, and from the booklet “Observing, Sandra L. Mason, Photographing and Collecting Plants” written by Robertson. Information on plant growth and development is adapted from University of Illinois Extension Educator, Extension’s Master Gardener manual. Additional editing and text were Horticulture & Environment contributed by Sandra L. Mason. Champaign County Chapter Goals After completing this chapter, volunteers should be able to: r Describe the basic characteristics of a plant. r Illustrate the correct way to designate scientific names. r I dentify and explain functions of major plant parts: roots, stems, leaves, and flowers. r Become familiar with a variety of leaf, flower, and fruit types to assist in identifying plants. r Successfully use a dichotomous key. r D escribe plant processes: photosynthesis, transpiration, and respiration. r U nderstand pollination and become familiar with different pollination mechanisms and methods of seed dispersal. r Describe seed germination. Botany 4-BOTANY Botany is the study of plants. What is a plant? The answer is not as simple as you might think. Most familiar plants: l Are green, contain chlorophyll, and manufacture their food through the process of photosynthesis. l Are immobile and rooted to the ground. l Have neither a nervous system nor an excretory system. l Have a cell wall composed largely of cellulose. l Can continue to grow almost indefinitely by cell division. However, some plants, including dodder, Indian pipes, beech drops, and cancer root, lack chloro­phyll and parasitize other plants. Other plants, such as Venus’­ flytrap and pitcher plants, trap and “digest” insects. These are examples of specialized flowering plants. Plants and People Have you thanked a green plant today? Plants are of enormous benefit to humans. As a matter of fact people and all other animals are totally dependent on plants for their existence. Plants are the only living organisms that are able to convert light energy into chemical energy. In the process of photosynthesis, carbon dioxide and water—in the presence of light—are made into simple sugars, which are the essential building blocks for all life as we know it and for nearly all sources of fuel energy, such as wood and the fossil fuels: coal, oil, and natural gas. In addition, the energy stored in sugars is the only source of energy to sustain living organisms. Without green plants, all animal life would cease to exist. Yet, food from crops is only one of the many plant products useful to people. What plants provide can be summed up with these categories. 4- Master Naturalist Program ©2006 l Food l Fiber/Fabrication l Fuel l Pharmaceuticals l Fermentation l Flowers/Forests/Fancification l Fragrance Food — We obviously eat plants but the animals we may also eat rely on plants for their food. Plants also make our food taste better. What would our food taste like without spices such as pepper, garlic, nutmeg, mustard, cinnamon, parsley, sage, rosemary, thyme, vanilla, cocoa, and many others, all of which are plant products? How many of us can do without sugar from sugar cane and sugar beets, coffee or chocolate? For centuries people have appreciated the development of beer, bread, wine and cheese with the help of plants. Fiber and fabrication — Before the development of synthetic products such as nylon, orlon, and plastics, people were dependent upon plants for fibers and building ma­terials. Wood products were, and still are, a major source of construction materials. Nearly all of the written and printed matter produced through history has depended on the use of paper products derived from plant fibers or wood. Fibers from the cotton, flax, and hemp plants and wool from animals grazing on plants were the major textiles used for cloth. Even synthetics are in most cases plant products since most are made from petroleum or coal, which are remnants of plants from millions of years ago. Before synthetic rubber was developed during World War II, the United States and the world rolled on tires made of latex from the sap of the rubber tree. Latex is still widely used for surgical tubing and many other products that require its unique properties. Fuel — Wood was once an important fuel, and still is in some parts of the world. All fossil fuels (coal, gas and petroleum) are the product of photosynthesis that took place several hundred million years ago. The problem with using fossil fuels today is that this releases carbon back into the atmosphere that has been stored as organic compounds all this time. Plants are often mentioned in long-range plans to help mitigate the energy crisis because they are a “renewable resource,” unlike the fossil fuels. Biofuels and biodiesels from a variety of plant sources such as soybeans, grains, vegetable oil, sugar cane, and grasses may prove to be important alternatives to petroleum Botany 4-products. Pharmaceuticals—Some plant products such as alcohol (produced by fermentation of sugar), tobacco, and drugs like heroin from the poppy, cocaine from coca and marijuana from the hemp plant have often been put to less than desirable uses by people. Many other drugs derived from plants are widely used in medicine. A good example is digitalis from the foxglove plant, often prescribed for patients with heart ailments. Plants with medicinal properties have been consumed by people for centuries. Plants provide beauty, shade from summer sun, wind protection, animal habitat and lovely fragrance. Stop and look around you at all the things that make up your everyday ­ world. How many have been derived from plants or plant products? How desirable would the world be without trees, shrubs, flowers, and grass that color and soften our world and ease the tensions of everyday life? Plants are worth knowing and appreciating for they are indispensable to us in every way. Although people have reached the moon, they have not yet found a substitute for a living plant. Major Plant Categories and Associated Groups l Flowering plants (angiosperms) l Conifers (gymnosperms) l Ferns, horsetails and club mosses l Mosses and liverworts l Algae l Fungi l Lichens In this chapter, the emphasis is on the flowering plants, since these are the most conspicuous and economically important plants. However, brief discussions of other plant categories and their associated groups are included. 4-4 Master Naturalist Program ©2006 however, ginkgo is a conifer with broad leaves. Conifers thrive particularly in the cooler regions of the temperate zones and make up much of the northern forests of North America and Eurasia. Many conifers are important ­ as ornamentals and for their wood products. Pine, spruce, fir, juniper, arborvitae, red cedar, yew, ginkgo, cypress, hemlock, redwood, and Douglas-fir are gymnosperms. Ferns, Horsetails, and Club Mosses Ferns, horsetails, and club mosses, collectively called the pterido­ phytes, have true roots, stems, and leaves; however, they lack flowers and seeds, and modern species do not produce wood. They reproduce by tiny spores, and many multiply vegetatively by creeping underground stems. Typical ferns have large, usually compound leaves, a stem that is an underground rhizome, and roots that grow profusely from the rhizome. Ferns are widely distributed in temperate and tropical regions, and since most cannot withstand drought or bright sunlight, they are usually restricted ­ to moist shaded habitats, such as forest floors and ravines. The horsetails, once abundant in past geological ages, are represented today by a single genus, Equisetum. They have perennial underground rhizomes and mostly annual above-ground stems or canes that are hollow, ribbed, jointed, and impregnated with silica. Pioneers used the stems to scour pots and pans, and some people call these plants “scouring rushes.” Horse­tails are found in wet, often sandy or gravelly soils of damp woods, along the banks of fast-moving rivers and streams, and in standing waters of rivers, ponds, and lakes. Club mosses are small, evergreen, perennial herbs with upright or trailing stems and small, simple, spirally arranged leaves. They are found mostly in acidic soil of moist, shaded woods and in bogs, and are especially abundant in the tropics. Some species are sold com­ mercially for use in Christmas decorations. Mosses and Liverworts Mosses and liverworts, collectively called the bryophytes, are small green plants that lack true roots, leaves, and flowers. They reproduce by spores. Mosses are only a few inches tall and grow in crowded clusters, tufts, or mats. Their plant bodies are stem-like with leafy scales and stalks bearing tiny capsules, which contain the dust-like spores. Mosses are cosmopolitan in distribution, but tend to prefer harsh habitats, such as exposed rocks, bogs, swamps, tree bark, forest 4- Master Naturalist Program ©2006 floors, decaying logs, areas around waterfalls, dim caves, cracks in city sidewalks, high altitudes, and the arctic tundra. The most familiar moss product is sphagnum peat moss, which is cut in large blocks from extensive peat deposits that are found at northern latitudes. Peat is used in soil mixtures and, particularly in northern Europe, as a fuel in stoves. Liverworts are of two general kinds. The first grows flat and ribbon-like on wet soil, damp rock, or even on the surface of water, sometimes forming shiny green carpets along streams and ledges. The second kind has distinct stems with leaf-like scales and grows flat or in mats on moist soil, decaying logs, or tree bark. Algae The algae include both the smallest and simplest of green plants as well as the giant kelps, which are among the largest of plants. Algae can be green, red, brown, yellowish, or purple, depending on the pigments in their cells. The green algae are grass green in color, may be one-celled, colonial, or filamentous, and are among the most widely distributed of all the algae, with species usually inhabiting fresh water and forming large colonies on the surface. They are important as a source of food for fish and other aquatic animals. Sometimes they become so abundant that they pollute waters, give off vile odors, choke streams, and clog filters in water purifying facilities. The yellow-green and golden-brown algae are found most often in cold brooks, mountain streams, and springs. The related diatoms are important food for fish, and are so abundant in marine waters that they are called the “grass of the sea.” The empty, beautifully ornamented siliceous walls of dead diatoms settle in marine waters and often accumulate, forming diatomaceous earth, which is used as a mild abrasive in polishes, cleansers, and toothpaste, and in insulation. The blue-green algae have blue and red pigments as well as chlorophyll and are found in a variety of habitats, with most species in fresh water, although a few are marine and some thrive in damp and shaded places, such as on the surfaces of soil, rocks, and flower pots. Some blue-green algae have the ability to “fix” atmospheric nitrogen into organic compounds. ­ The brown algae, which include the giant kelps, have yellow, orange, or brown pigments and are almost entirely marine. They prefer cool water and are especially Botany 4-abundant in the Arctic and Antarctic oceans and along the coasts of the North Atlantic and North Pacific. Brown algae are important food for fish, are used in cattle feed, and are eaten by many people in Asia. Some brown algae are harvested for their abundant gelatinous compounds, which are used in ice cream, laxatives, and cosmetics. The red algae have a unique reddish pigment and are mostly marine, although a few species occur in fresh water. Fungi Fungi are a group of organisms that lack chlorophyll, roots, stems, leaves, and flowers. Once considered plants, they are now classified in their own group. Fungi reproduce by means of spores, are usually filamentous, have definite cell walls, and live a saprophytic or parasitic existence. As saprophytes they share with bacteria the role of decaying the remains of dead organisms, and as parasites they cause diseases in plants and animals. The large fleshy fungi, such as mushrooms, toadstools, bracket fungi, and puffballs, are familiar to everyone who has walked the Illinois countryside. Other fungi include the morels, truffles, earthstars, and bird’s nest fungi. Most fungi are microscopic and not visible to the naked eye, such as molds, mildews, yeasts, rusts, and smuts. Mushrooms produce a fruiting body that consists of a stalk surmounted by a broad, umbrella-shaped cap. The reproductive spores are produced on the sides of gills located on the underside of the cap. The mushroom is only one part of the body of the fungus: think of a mushroom as the apple on the tree. The remainder consists of an extensive mass of threadlike filaments (hyphae) that grow hidden in the soil or other sub­strate. Technically, there is no difference between a mushroom and a toadstool. By tradition, the term “mushroom” refers to edible species, some highly prized for their delicious flavors and aromas. The term “toadstool” ­ is used for poisonous species, which produce toxic compounds that can cause illness or death. Since both edible and poisonous species can occur together and can resemble each other, there is great danger of amateurs ­ confusing safe and toxic species. Only people who are thoroughly familiar with the technical identification of mushrooms should collect and eat wild species. The bracket fungi resemble mushrooms but differ in having pores instead of gills and are often asymmetrical and hang, bracket-like, on dead or living tree trunks. The puffballs produce round or pear- shaped fruiting bodies with a conspicuous outer covering, liberat­ing spores at maturity through a pore or break at the top of the ball. 4- Master Naturalist Program ©2006 Some puffballs can reach the size of a basketball. They are found on decomposing wood and bark, decaying leaves, and animal wastes. Mushrooms can be found throughout most of the year, but the largest number appear with the cool moist weather of autumn. This diversity will last until temperatures fall below freezing. Warm spring temperatures combined ­ with moist weather bring out the second largest number of fleshy fungi, including many gilled and pore fungi, morels, and puffballs. In late spring and summer, the number of fleshy fungi drops to a low point. A cool spell in August, accompanied by showers, will bring out large numbers of puffballs and pore fungi. However, the return of hot weather will quickly reduce the numbers to a few scattered specimens. Fungi, besides being tasty additions to pizza, are important additions to our medicines and food. Many antibiotics, including penicillin, ­ streptomycin, terramycin, aureomycin, and chloromycetin, were originally produced ­ by fungi. Yeasts carry out the process of fermentation, which makes possible bread, alcoholic beverages, and vinegar. Fungi are also important in the ripening of certain kinds of cheese, such as Roquefort, Camembert, Brie, and Stilton. Lichens Lichen is a unique organism composed of a microscopic green or blue-green alga and a colorless fungus. The alga and fungus live together in a mutually beneficial association termed symbiosis. The plant body that is formed has no resemblance to either the algal or fungal component. ­ The algal partner provides food energy through photosynthesis and the fungal partner lives on this food, makes up the bulk of the plant body, protects the alga from desiccation, absorbs mineral elements and water, and synthesizes many essential organic compounds. Lichens have a cosmopolitan distribution and are found on a great variety of substrates, ­ such as rock, trees, wood, and soil, from the Arctic (where they are dominant in the tundra) to the Antarctic, from sea level to alpine habitats, in deserts, and in freshwater and marine environments. People are often concerned when they see lichen on the bark of tree trunks. The lichen neither harms nor helps the tree. Some lichen communities last for centuries in the Arctic and Antarctic, but if the environment is disturbed, they are eventually replaced by mosses, liverworts, and plants. Lichens are very sensitive to air pollution, and different species are affected by different concentrations of specific air pollutants. Thus, it is frequently possible to estimate the level of air pollution in an area by Botany 4-Plant Classification With at least 500,000 different kinds of plants in the world, it is necessary to organize this diversity into a classification scheme to be able to communicate with others. There are a variety of ways plants can be classified, such as alphabetically (hibiscus, hickory, hollyhock, hydrangea); by growth habit (herb, shrub, tree, or vine); by habitat (aquatic, terrestrial, aerial); or by shared characteristics (white flowers, opposite leaves, edible fruits). However, the classification system that has been most useful to botanists is one that groups related plants together into a series of hierarchical categories, so that very closely allied plants are placed together in the system, plants that are somewhat related are grouped near each other, while plants that have very little in common are placed far from each other. The classification scheme used for plants has the following categories: ­ Division Class Order Family Genus Species Subspecies Variety Form Cultivar The basic unit of classification is a species. It is impossible to precisely define a species so that the definition would apply to all plants and be agreed upon by all botanists. In general, however, a species is a population or a series of populations whose individuals are distinct and distinguishable from indi­viduals of other such populations, this distinctiveness is self-perpetuating through succeeding generations, and the population(s) is usually re­productively isolated from populations of other species. To the layperson a species is a particular kind of plant or, put another way, all individual plants that look more-or-less alike constitute a species. The word “species” is both singular and plural. Botany 4-We intuitively recognize some species. All humans constitute a species, and white oak, eastern redbud, flowering dogwood, and white pine are familiar tree species. Variation does exist within species, and these variants are sometimes recognized either as subspecies, varieties, or forms (depending on the magnitude of the variations) if they occur in the wild, or as cultivars or lines if they occur only in cultivation. Related species are grouped together into genera (singular, genus). Again, the layperson perceives this. For instance all oaks belong to one genus, roses to another, and pines to a third. Some species are so distinctive that they are placed in a genus by themselves, as is the case with the ginkgo tree. Related genera, in turn, are placed in the same family. This category has no equivalent among laypeople, yet it is one of the most useful to botanists. It is relatively easy to learn the identifying characteristics of common plant families in Illinois, and this knowledge is of immense use in quickly identifying unknown plants. Among the common families in the state are: the grass family, the lily family, the mustard family, the rose family, the legume (or bean) family, the carrot family, the mint family, and the aster (or sunflower) family. Approximately half of the world’s families of ferns, conifers, and flowering plants occur natively or naturalized in Illinois, and a number of other families are cultivated. A person with a knowledge of the characteristics of plant families in Illinois can go nearly anywhere in the world and recognize the families of the majority of plants. Plant Names Since ancient time, people have given names to plants that are of special interest, such as food plants, fiber-producing plants, poisonous plants, and ornamental plants. There are two kinds of names given to plants: common names and scientific names. The two names are complementary and each has a definite purpose. Common Names Common names are used by the general population of a given region and are nearly always in the language spoken locally, i.e., English in Illinois, French in Quebec, and Spanish in Mexico. Common names are the only names by which most people know familiar plants, since they are usually composed of everyday words. They also are often 4- Master Naturalist Program ©2006 easy to remember, can accurately depict outstanding characteristics of a plant, and can be precise and stable within limited geographical areas. How­ever, the use of common names has several drawbacks. The same common name may be used for more than one kind of plant, both within one area and from place to place. For example, “mayflower” is the name used for a member of the lily family (the scientific name of this plant is Maianthemum cana­dense) and also for a member of the heath family (Epigaea repens). Nearly everyone in the United States uses the name “corn” for the plant known botanically as Zea mays; however, in Europe, “corn” is used for any kind of grain. Also the same kind of plant may have more than one common name. In addition to being called “mayflower,” Maianthemum canadense is also called “wild lily-of-the-valley,” and Zea mays is called “maize,” particularly in Europe. As another example, the name “adder’s tongue” can refer either to a quaint fern, Ophioglossum vulgatum, or to a lovely member of the lily family, Erythronium albidum. The latter is also known as “trout- lily,” “fawn-lily,” or “dog-tooth-violet.” Scientific names mitigate the ambiguity created by the use of common names. Scientific Names The science of botany in Europe, particularly the aspect of identify­ ing and naming plants, reached full development in the eighteenth century. At that time, educated people in all fields, from law, medicine, philosophy, and religion to science, used Latin as a universal language, which greatly facilitated communication between people of different nationalities speaking ­ many native languages. Thus, it was only natural that Latin was used for plant names in learned circles. At first, plants were given descriptive phrase names such as Rosa carolina fragrans, foliis medio tenus serratis. These names were long, confusing, and difficult to remember, and in 1753, the Swedish botanist Carl Linnaeus applied a system of naming to the entire plant kingdom whereby a plant name consisted of only two words. This binomial system is still used universally by scientists, now following the strict rules of the International Code of Botanical Nomen­clature. The first word of the scientific name is the name of the genus to which the plant is assigned, and the second word is the specific epithet. Thus, from the examples above, Maianthemum is the name of the genus and canadense is the specific epithet, and together, Maianthemum canadense, they make the scientic fi name, Botany 4-also referred to as the species. These names are always in Latin or, if derived from other languages, treated as if they were Latin. Scientic fi names are underlined when handwritten and italicized or underlined in print. The r fi st letter of the generic name is always capitalized; that of the specic fi epithet may always be left uncapitalized, although it can be capitalized if the name commemorates a person or an old generic name. The generic name refers to a general kind of plant while the specic fi epithet indicates a particular kind of plant. Thus, the genus Rosa is used for all kinds of roses, while Rosa setigera is the prairie rose. When the generic name is frequently repeated, it is customary to abbreviate it by the r fi st letter. Accordingly, Rosa carolina is the pasture rose, R. centifolia is the cabbage rose, and R. canina is the dog rose. These examples show that the use of two words for the name of a particular kind of plant is not restricted to scientic fi names, but that we frequently do this in English with one word modifying the other. Following the name of the species is the name of the person who gave the plant that name. This is a bibliographic aid to help locate additional information about the name. Many plants in the eastern United States were r fi st named by Linnaeus, for instance, Rosa carolina Linnaeus, the pasture rose. Certain people described so many plants that their name is abbreviated, such as Rosa carolina L., R. canina L., and R. setigera Michx. (for Michaux). Some o fl ras give lists of author abbre ­ viations. Sometimes a species may have two or more recognizable variants. As previously mentioned, if these are discovered in wild plants, they are called subspecies, varieties, or forms—depending on the magnitude of the variations—and are given an additional Latin name. For example, the pasture rose R. carolina has two variants, one with the leaves smooth and the other with the leaves quite hairy beneath. The r fi st one is called R. carolina var. carolina and the second, R. carolina var. villosa. Author citations are used with these names when the name of the variant is differe ­ nt from that of the species, as in R. carolina L. var. villosa (Best) Rehd ­ er. When variants occur only in cultivated plants, they are given cultiv ­ ar names, which may be in languages other than Latin, and they do not carry an author citation with them. The cultivar name is placed in single quotation marks after the specic fi name, or, in some cases, after the generic name. Cultivar names are capitalized, but not italicized. For example, the name of the Bradford pear is Pyrus calleryana ‘Bradford.’ It is never correct to 4-4  Master Naturalist Program ©2006 use so-called trinomial names, such as Rosa carolina villosa, that do not indicate the classic fi ation rank of the third name. The names of plant families are based on the name of a genus with the ending changed to “-aceae.” Thus, Rosaceae is the name of the rose family and Liliaceae of the lily family. A few very common families may be called either by their traditional name or by the name that is based on the name of an included genus. Thus, the grass family is Gramineae or Poaceae; the legume or bean family is Leguminosae or Fabaceae; the mustard family is Cruciferae or Brassicaceae; the mint family is Labiatae or Lamiaceae; the carrot family is Umbelliferae or Apiaceae; and the sunflower family is Compositae or Asteraceae. The International Code of Botanical Nomenclature establishes one set of rules by which plants are named. According to these rules, no two kinds of plants can have the same name, and under a given genus, a species can have only one correct name. This correct name is the combination of the earliest correct generic name with the earliest specific epithet. Some people wonder why one book will use one scientic fi name for a plant while another will use a different name for the same plant. There are basically three reasons for this. The first is that there has been a name change made necessary by the rules of the International Code of Botanical Nomenclature. The second reason is that some groups of plants are more difc fi ult to classify than others, and different authors may classify them differently. The third reason is that modern molecular data may indicate that two groups formerly considered related to each other, and thus placed in the same genus or family, may not be related at all; as a result species can be transferred to different genera, and the circumscription of genera and families may be quite different from their traditional delimitation. Pronunciation of Scientific Names Many people who would use scientific names are afraid to do so because the words seem difficult to pronounce. A number of generic names have become adopted as common names and are familiar to most people — Chrysanthemum, Geranium, Rhododendron, Magnolia, Aster, Catalpa, Phlox, Iris, Trillium, Delphinium, Sassafras, and Hydrangea. There are many common names that are very similar to the scientific names: such as lily, Lilium; rose, Rosa; alder, Alnus; spirea, Spiraea; violet, Viola; gentian, Gentiana; elm, Ulmus; pine, Pinus; poplar, Populus; larch, Larix; Botany 4-and juniper, Juniperus. All of these words are easy for most people to pronounce because they are familiar with them. Other scientific names may take a little practice. Actually, most Latin or Latinized words are easier to pronounce than unknown English words. Finally, there is no need for someone to be afraid of “mispronouncing” ­ scientific names because there are several different systems for pronouncing Latin - “traditional English” pronunciation as used by most botanists and horticulturalists in English-speaking countries, “re-formed academic” attempts to approximate the pronunciation of educated Romans, and Latin as used in the Catholic religion. In this country most letters of the alphabet are pronounced the same in Latin as in English, including the consonants b, c (hard and soft), d, f, g (hard and soft), h, k, l, m, n, p, q, r, s (always as in so, not like z), t, v, and z. The letters j, u, and w were not in the classical Latin alphabet; when they appear in Latinized words, they are usually pronounced as in English except that j sometimes has the sound of y in yellow. The letter x at the beginning of a word has the sound of z; for example, Xanthium is zăn´-thē-ŭm and Xyris is zī´-rŭs. Elsewhere, x is pronounced as in Eng­lish, such as Larix is lăr-iks and Oxalis is ŏks-ă´-lis. All vowels may be either long or short, as in English. A Latin word has as many syllables as it has vowels or diphthongs (two vowels pronounced as one sound). The diphthongs commonly used in botanical names, and their pronunciations, are: ae (ē as ea in meat), au (as aw in awful), and eu (as in neutral and as oo in tool). Some examples are: Actaea (ăk-tē´-ă), laevis (lē´-vis), Aureolaria (ăw-rē-ō-lār´-i-ă), ­ caudatus (kăw-dā´-tŭs), Eleusine (ĕl-ōō´-si-nē), and Deutzia (dōōt´-zē-ă). Every vowel or diphthong is pronounced, and there are no silent letters at the end of a word. Thus, Ribes is rī´-bēs, not ribs or rībs; Androsace is ăn-drō-sā´-sē; Leucothoe is lōō-cō´-thō-ē; gerardii is jĕr-ăr´-dē-ī; illinoense is il-li-nō-in´-sē; Rosaceae is rōs-ā´-sē-ē; Liatris is lī-ā´-tris; Illiama is il-lē-ă´-mă; and Aloe is ă-lō´-ē, not ăl-ō. When a word begins with any of the following combinations of two consonants, the first letter is silent: cn, gn, mn, ps, and pt. Thus, Cnicus is nī´-kŭs; Gnaphalium is nă-fā´-lē-ŭm; Mnium is nī-ŭm; Psoralea is sō-rā´-lē-ă; and ­ Pteridium is tĕ-ri´-dē-ŭm. 4- Master Naturalist Program ©2006 Plant Identification Plant identification is basic to the study of plants. Once a plant is identified, a wealth of information, such as life cycle and associated plants, may be available about the plant. You can also communicate with others about the plant. Obviously, it is extremely important to iden­tify the plant correctly, for if it is misidentified, then any information you learn or pass on about the plant may be misapplied. As an extreme example, mistaking a foxglove plant for the herb comfrey can be life threatening. There are several ways to identify a plant. The simplest, and often the best, is to ask some knowledgeable person. Another way is to compare the plant with photographs, drawings, or descriptions in guidebooks or floras, which need not require much technical knowledge, but which can be very time consuming. If one has access to a herbarium col­lection, unknown plants can be compared to already named specimens. Lastly, plants can be identified with the use of “keys” for identification that are found in nearly all floras or botanical manuals. Because of the large number of categories of plants, there is no single book to use to identify all plants; rather, different books are used for different kinds of plants. The following are common categories: l Food plants and edible wild plants—Usually well- illustrated and often containing information on how to prepare edible wild plants. l Floras and manuals—Generally include all species of flowering plants, conifers, and ferns for particular geographical areas; nearly all contain keys, some are illustrated. l Wildflowers —Contain the most common species that occur in particular geographical areas; nearly always well illustrated with draw­ings and/or photographs; rarely with keys. l Weeds—Similar to wildflower books, but for weeds; wildflower and weed books may include some of the same plants. l Woody plants—Contain the means to identify native and/or cultivated trees, shrubs, and woody vines; some with keys, some with illustrations or photographs, some with neither. l Cultivated plants—Like the preceding, but for garden flowers, house plants, and other cultivated plants. l Special habitats—A few books deal with plants in particular Botany 4-habi­tats, such as prairies and aquatic situations. l Specific plant groups —Separate guidebooks are available for: grasses, orchids, ferns, mosses, liverworts, lichens, fungi, and algae. Professional taxonomic botanists usually have a number of books for identifying plants, and botanical libraries contain thousands of such books. However, a student or layperson is usually only interested in a few categories of plants, such as wildflowers or trees, and can identify most plants with a few titles. Most public, school, and university libraries have a number of the different identification books. Keys By the use of keys, plants that have particular structural features are separated from all plants that lack such features, and the process of identification is made simpler. A key consists of a series of paired contrasting or contradictory statements: each pair of statements is called a couplet. The first couplet of a key is compared with the plant to be identified. One of the statements will not apply to the plant while the other one will, and leads to another set of couplets. This process of choosing one statement of a couplet and rejecting the other is repeated until only one possibility remains, which gives the name of the plant. This process is called keying out a plant. Most books have a number of separate keys. One key is used to determine the plant family (if it is not known), another to identify the plant to genus, and a third key to identify the species. With experience, common families and genera are readily recognized, which makes the identification to species much more rapid. Often, however, all is not so simple, and the user may not have all the information needed to select the proper statement, or the choices are not clear-cut. Nevertheless, time has proven the usefulness of keys. With experience, keys become relatively easy to use, and you will be able to take pride in your ability to use them. 4- Master Naturalist Program ©2006 Hints for the Use of Keys 1. Examine the unknown plant in a general way to see its basic morphological features, such as habit, leaf type and arrangement, flower color and structure, and fruit type. An important skill in plant identification is educating your brain and your eye as to what attributes should be noted. This will save time when using the key; certain other features will have to be checked more thoroughly while using a key. 2. Select a suitable key. This is very important. Use a key that is as specific as pos sible. ­ For instance, if trying to identify a plant from a pond in Illinois, it would be best to use a book dealing with aquatic plants of Illinois; a flora of Illinois or a manual on aquatic plants in general would be next best; while a flora of the entire eastern United States would be consid­erably more difficult. 3. Look carefully at the key to determine its arrangement and read any instructions on the use of the key. 4. Always begin at the very first couplet; sometimes it is tempting to jump to the middle of a familiar key. 5. Read carefully both statements of a couplet before selecting one. 6. Use a glossary for any terms you don’t understand; remember that the same term may have different connotations for different authors. 7. When measurements are called for, make them carefully and don’t guess. Measurements should be made from several samples. 8. Use a hand lens when the key asks about minute structures. 9. Remember that there is variation within a species; most keys ap­ ply to the usual situation and may not include extremes. 10. When it is not clear which statement of a couplet to select, choose the one that best suits the unknown plant; it is not always possible to write keys that perfectly fit every plant to which the statement is sup­posed to apply. 11. When it is seemingly impossible to select one statement over another or not enough information is at hand, arbitrarily select one statement and proceed for several other couplets, then go back and try the other troublesome statement and follow it for a few additional couplets. ­ Usually, it will become obvious which of the two statements is the correct choice. 12. Once a tentative identification is made with a key, check the identification with detailed descriptions, illustrations, photographs, and if possible, with accurately identified herbarium specimens. 13. Check the geographical and habitat descriptions to make sure the plant being identified occurs in the same region and habitat as the species to which it has been tentatively identified. Botany 4- A Simplified Yoked Key to Separate Certain Genera of Common Trees 1. Leaves alternate. 2. Leaves simple. 3. Leaves fan-shaped with a notch at the tip ....Ginkgo. 3. Leaves not fan-shaped, lacking a notch at the tip. 4. Leaves entire ..........................................Magnolia. 4. Leaves lobed or toothed. 5. Leaves lobed .....................................Quercus. 5. Leaves toothed..................... ..................Ulmus. 2. Leaves compound. 6. Leaflets small ................................................ Gleditsia. 6. Leaflets large ............................................... Cladrastis. 1. Leaves opposite or whorled. 7. Leaves whorled ............................................... Catalpa. 7. Leaves opposite. 8. Leaves simple. 9. Leaves palmately lobed ........................... Acer. 9. Leaves entire ........................................Cornus. 8. Leaves compound. 10. Leaves palmately compound ......... Aesculus. 10. Leaves pinnately compound ............................Fraxinus. 4-0  Master Naturalist Program ©2006

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