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Botany Handbook for Florida1

Sydney Park Brown and Kathleen C. Ruppert 2

Introduction

Ivy, maple, azalea, spider plant—these names are as familiar to us as old friends, yet very few people bother to learn their scientific names. This is unfortunate because the two-word names (binomials) given to plants are often colorful and descriptive. The genus and species names of plants have been compared to the first and last names of people—there may be many Janes, but they are divided into Jane Smith, Jane Jones, Jane Johnson, and so on. Similarly, there are many species of Quercus (oaks), but only one Quercus virginiana (live oak). The species name is a very specific adjective or noun that narrows an entire genus to just one plant. Consider the examples given in Table 1.

Table 1. 

Examples of common name, scientific name and meaning of scientific name.

Common Name

Scientific name

Grape Ivy

Cissus

rhombifolia

 

ivy

diamond-shaped leaves

Red Maple

Acer

rubrum

 

maple

red

Sweet Gum

Liquidambar

styraciflua

 

liquid amber

flowing with gum

Pink Pinxter Azalea

Rhododendron

canescens

 

rose tree

off-white hairs

Spider Plant

Chlorophytum

comosum

 

green plant

tufted

As you can see, learning the scientific names of plants can be interesting. After working with these names a while, you will recognize certain prefixes, suffixes, and word roots and be able to identify plants by physical characteristics that match their names.

Plants that are very similar are often in the same family. Therefore, knowing the family characteristics can sometimes significantly narrow the identification process. The first step for identification when you have the actual plant in front of you is to examine characteristics of its parts, such as the stems, leaves, flowers, fruits, and seeds.

This handbook will assist you in learning the terms used to describe these characteristics, with clear, concise definitions and examples, and is an invaluable tool for the beginning botanist.

Chapter 1: The Plant World

The plant world is extremely diverse, ranging from one-celled algae to huge oaks and sequoias. It contains plants such as mushrooms, which have no green coloring, and lichens and mosses, which are green plants but have no true roots and leaves and no flowers. Many gardeners grow ferns of various kinds. They are green plants with true leaves and roots but no flowers or seeds; instead, they reproduce by means of spores. And, finally, there are the seed-bearing plants, which make up the vast majority of the plant kingdom. It is with this group of plants that this handout is concerned.

Spermatophytes (Seed Plants)

Spermatophytes are plants that produce true seeds, each containing an embryo (a minute, inactive plant) that germinates (begins to grow) under favorable conditions. Seed-bearing plants have true leaves, stems, roots, and vascular tissue. These plants constitute the greater part of the vegetation on earth. They consist of two classes, the gymnosperms and the angiosperms .

Gymnosperms (Cone-bearing plants and their allies)

Gymnosperm means "naked seeded." All gymnosperms are woody, perennial, and, with few exceptions, evergreen plants. The reproductive organs are borne in structures called catkins or in cones with the seeds usually uncovered. Their leaves may be fern-like, scale-like, strap-shaped, or needle-shaped. This group is represented today principally by the cone-bearing trees (conifers) and palm-like plants (cycads). Examples of plant families that are gymnosperms include the following:

  • Cupressaceae - Cypress family - Juniperus spp. (e.g., junipers); Taxodium spp. (e.g., bald cypress)

  • Cycadaceae and Zamiaceae - Cycad family - Cycas spp.(cycads); Zamia spp. (coontie)

  • Ginkgoaceae - Ginkgo family - Ginkgo biloba (e.g., maidenhair tree)

  • Pinaceae - Pine family - Pinus spp. (e.g., pines); Cedrus spp. (e.g., true cedars)

  • Podocarpaceae - Podocarpus family - Podocarpus spp. (e.g., podocarpus)

  • Taxaceae – Yew Family -Taxus floridana (Florida yew); Torreya taxifolia (e.g., Florida torreya)

Angiosperms (Flowering plants)

The angiosperms include those species that have flowers and seeds always protected by a fruit. They form a large, complex group of flowering plants under two main divisions: the monocotyledons (monocots) and the dicotyledons (dicots). These divisions are based upon the number of cotyledons, or "seed leaves," found in the seed.

The monocotyledons have one cotyledon (seed leaf) in the seed. Generally they have parallel-veined leaves and flower parts in 3's (or in multiples of 3's, but never 4's or 5's). Their stems are made up of vascular bundles without pith or bark. A few of the monocots, such as bamboos and palms, are tree-like. The majority, however, are herbaceous plants such as grasses, lilies, irises, orchids, bananas, and bromeliads.

Dicotyledons have two cotyledons in the seed. They can be recognized by their net-veined leaves and by their flower parts (sepals, petals, stamens, and pistils), which are generally in 4's or 5's or multiples of 4's or 5's. Some dicots, such as willows and poplars, have many small flowers without petals or sepals called catkins. Others have flowers with separate petals and sepals, such as Rosa spp. (rose) and Magnolia grandiflora (southern magnolia). Still others have flowers in which the petals or sepals or both are fused to form a trumpet-shaped flower, such as Lonicera spp. (honeysuckle) and Allamanda cathartica (allamanda).

Chapter 2: Root Systems

The functions of roots are to act as support for the stem, to absorb and conduct water and nutrients from the soil, and to store food. Root systems consist of a main or primary root, rootlets or secondary roots, and root hairs.

The primary root arises from the seed embryo. Branches of the primary (tap) root are often fibrous and are called secondary roots. The primary root system of many plants is short-lived and is eventually replaced by a secondary root system. These secondary root systems become the permanent roots of many monocots such as the grasses. Roots coming from bulbs, corms, rhizomes, or tubers (see Chapter 4) are adventitious roots. Stolons and runners and cuttings from stems or leaves also develop adventitious roots. Rhizophora mangle (red mangrove), Pandanus spp. (screw-pine), and Ficus spp. (banyan) send down adventitious roots that become supports for heavy, horizontal branches.

Root hairs are thin hair-like outgrowths of a plant root that penetrate into the openings between soil particles and absorb water and minerals from the soil. Water and soluble nutrients enter the root hairs, pass into the rootlets, and travel through the main root into the stems and leaves. Root hairs are formed in great numbers near the tips of roots. In most plants they are short-lived. If a plant is transplanted carelessly, it is the loss of many of these small root hairs with their water-absorbing cells that will cause the plant to wilt.

Tap roots are prominent primary roots from which all other lateral rootlets or secondary roots grow. They may divide, become fleshy, and often penetrate deeply into the soil.

Fibrous roots are adventitious, have no distinguishable primary root, and are composed of a number of fine, thread-like roots of the same kind and size, originating at the base of the stem. Fibrous roots often spread out near the surface of the soil rather than penetrating deeply.

Fleshy roots act as food reservoirs for plants during adverse periods. Daucus carota (carrots), Brassica rapa (turnips), and Beta vulgaris (beets) have primary or tap roots containing food. Ipomoea batatas (sweet potatoes) and Dahlia spp. (dahlia) have secondary roots modified into tuberous roots packed with food.

Aerial roots form freely on many land and water plants growing in a moist atmosphere. These roots enable climbers such as Philodendron spp. (philodendrons) to attach themselves to a host. The aerial roots of air plants or epiphytes such as some orchids not only attach the plant to its host but also absorb water from the air. Many aerial roots are fleshy or semi-fleshy, functioning as reservoirs for water storage.

Knees (pneumatophores) are developed by Taxodium distichum (bald cypress) growing on swampy ground. These trees develop woody-knees that protrude above the surface to enable the plant to obtain air.

Chapter 3: Stems

A stem may be defined as a structure that develops from a bud to bear leaves — either full-sized or rudimentary — and buds. Stems have swellings at certain points called nodes. A node is the point on a stem where a leaf is or was attached. The area between nodes is termed the internode. Stems usually grow upward to the light but may grow underground (rhizomes).

The functions of stems are to support and display leaves, fruit, and flowers; to carry water and nutrients from the roots to the leaves; and to carry food produced by the green parts back to the roots. In plants that lack leaves, such as cacti, all food is produced in the green stem. Stems may be annual, biennial, or perennial, although some plants with perennial roots have annual stems.

Stems may be adapted for food storage, such as tubers, corms, bulbs, or rhizomes. They may also be specialized as runners, tendrils, or thorns. The tendrils of Vitis spp. (grapes) and Parthenocissus quinquefolia (Virginia creeper) are modified stems. (Keep in mind that in some species tendrils may be modified leaves.)

  • Crowns - short and inconspicuous stems. Such plants are said to be stemless or acaulescent, such as Gerbera spp. (gerbera daisy). Crown is also the name for the base of the stems where roots arise.

  • Simple - stems without branches (side growths), such as in Zea mays (corn).

  • Branched - stems with more than one terminal bud, with side growths or branches.

  • Climbing - stems too weak to support themselves, which lean or twist about other plants or posts for support, such as in Bougainvillea spp. (bougainvillea) and Pyrostegia venusta (flame vine).

Creeping - stems that rest on the surface of the ground, sending down roots at the nodes or joints, such as in the weed Sphagneticola trilobata (wedelia) and Lantana montevidensis (trailing lantana).

  • Rhizomes - prostrate, usually thickened, underground stems, with leaves coming from one side and roots from the other, such as Canna x generalis (canna) and some of the Begonia spp.

  • Stolons - slender, modified stems growing along the surface of the ground and rooting at the nodes, as in Fragaria x ananassa (strawberry) and Stenotaphrum secundatum (St. Augustinegrass).

Chapter 4: Food Reservoirs

Many plants accumulate food—sugars, starches, and other products—especially in fruits and seeds, and in modified roots and stems.

Fruits of various types (see Chapter 9) serve as food reservoirs. Examples are Malus spp. (apples), Prunus spp. (cherries), Mangifera indica (mangos), and Cucurbita spp. (squashes), as well as the one-seeded dry fruits of the grains, such as Triticum aestivum (wheat) and Zea mays (corn).

Seeds of such plants as Pisum sativum (English pea) serve as food reservoirs.

Roots accumulate food, such as the taproot of Daucus carota (carrots), Pastinaca sativa (parsnips), and Beta vulgaris (beets), and the tuberous roots of Ipomoea batatas (sweet potatoes) and Manihot esculenta (cassavas). These root tubers do not have buds or "eyes," but may produce adventitious buds that become stems.

Stems may be adapted as food reservoirs, as in the following examples:

  • Stem Tubers usually grow underground but have buds or "eyes" from which spring new stems, such as in Solanum tuberosum (Irish potato) or Caladium bicolor (caladium).

  • Corms are solid masses of stem tissue. They are actually a condensed stem with a bud on top from which the new stem grows. Gladiolus spp. (gladiolus) is an example of a corm.

  • Cormels are small corms that form around the base of a larger corm.

  • Bulbs are compressed stems containing a growing point (bud) or flower bud enclosed by thick, fleshy scale leaves. Bulbs such as Hippeastrum spp. (amaryllis) and Allium cepa (onion) are called tunicate bulbs because they are protected from drying and mechanical injury by dry and membranous outer scales called a tunic.

  • Other bulbs such as Lilium longiflorum (Easter lily) are called non-tunicate or scaly because their outer scales are succulent and separate.

  • Bulblets are small bulbs growing from the main bulb, such as in Hippeastrum spp. (amaryllis).

  • Bulbils grow on the stem in the axils of leaves or bracts. They may be small bulbs, as in some lilies, or leafy appendages, as in Alpinia purpurata (red ginger), Dietes iridioides (African iris), and Hemerocallis spp. (daylilies). Bulbils may be used for propagation.

  • Rhizomes can be a food reservoir and an easy means of propagation by division. Examples are Heliconia spp. (heliconia), Arundinaria gigantea (switch cane), and Pleopeltis polypodioides (Resurrection fern).

Chapter 5: Leaves

Evergreen plants have foliage that remains functional through more than one growing season, whereas deciduous plants shed all or nearly all their foliage each year. A typical leaf consists of two principal parts: the expanded leaf blade or lamina, and the slender petiole or leaf stalk. Frequently there are outgrowths at the base of the petiole known as stipules, which may be leaf-like, spines, or glands. In dicots and some gymnosperms, the leaf blade is a thin sheet of green tissue strengthened by the midrib and veins. There are three main types of venation in leaves:

  • Parallel venation - the veins run parallel to each other. This condition is characteristic of monocots. Parallel veins may run lengthwise on the leaf, as in Eucharis grandiflora (Amazon lily), or they may be parallel but directed outward from the midrib to the margin (penni-parallel).

  • Pinnate venation - leaves have a single primary vein or midrib, from which smaller veins branch off, like the divisions of a feather. Examples are Eriobotrya japonica (loquat) and Camellia japonica (camellia).

  • Palmate venation - leaves have several principal veins radiating from the base of the leaf blade (like the palm of your hand), as in Acer rubrum (red maple) and Carica papaya (papaya).

Leaf Forms

Linear - narrow, several times longer than wide, and essentially of the same width throughout.

Lanceolate - much longer than wide and tapering towards the apex from a broader base.

Oblanceolate - much longer than wide, tapering towards the base instead of the apex (the opposite of lanceolate).

Oblong - nearly twice as long as broad, with the sides nearly parallel or parallel most of their length.

Elliptic - oblong, broadest in the middle with the two ends narrowing.

Ovate - egg-shaped, with the broadest part near the base.

Obovate - opposite of ovate, with the narrower part near the base.

Cuneate - wedge-shaped, broad at the tip and tapering by nearly straight lines to an acute angle at the base.

Spatulate - oblong but tapering to a narrow base; spoon-shaped.

Sagittate - arrow-shaped; lobes at base acute and pointing downward, while the main body tapers upward to a point.

Leaf Bases

Cordate - heart-shaped.

Reniform - kidney-shaped, like cordate, but rounder and broader than long.

Auriculate - a small pair of projections, or ears, usually at the base.

Hastate – spear-shaped; lobes at base pointed and narrow and nearly at right angles to petiole.

Oblique - slanting, unequal-sided.

Leaf Tips

Acuminate - prolonged into a narrowed or tapering point.

Acute - ending in an acute angle, but not a prolonged point.

Obtuse - blunt or rounded apex.

Truncate - square end that looks cut off.

Emarginate - indented or notched.

Obcordate - inversely heart-shaped; an obovate leaf that is much more deeply notched at the tip.

Cuspidate - tipped with an elongated sharp or rigid point.

Mucronate - abruptly tipped with a small, short point, like a mere projection of the midrib.

Leaf Edges/Margins

Entire - even line, without teeth, notches, or lobes.

Serrate - cut into sharp, saw-like teeth pointing forward.

Dentate - toothed; teeth point outward instead of forward and are large.

Crenate - teeth are short and rounded; also called scalloped.

Undulate - margin of the leaf forms a wavy line, bending slightly inward and outward in succession.

Sinuate - like undulate, margin is very wavy (sinuous).

Incised - cut into sharp, deep, and irregular teeth or incisions.

Lobed - incisions do not extend deeper than halfway between the margin and the center of the blade and are rounded.

Cleft - incisions extend more than halfway between the margin and the center of the blade, and are sharper.

Deeply Lobed - incisions are even deeper, but not quite to the midrib or base of the blade.

Leaf Divisions

Simple - blade is of one piece, as in Camellia japonica (camellia). It may still be simple and lobed or cleft, as in Hibiscus rosa-sinensis (hibiscus), Quercus shumardii (Shumard oak), and Acer rubrum (red maple).

Compound - blade is made up of a number of separate leaflets. The two principal types of compound leaves are pinnate and palmate:

  1. Pinnate - leaflets or pinnae are arranged on the sides of the main leaf stalk. Examples are Nephrolepis exaltata 'Bostoniensis' (Boston sword fern), Roystonea regia (Cuban royal palm), and Zamia floridana (coontie).

    • Odd Pinnate - pinnate with an odd number of leaflets; has an end leaflet. Examples are Schinus terebinthifolius (Brazilian pepper), Wisteria sinensis (wisteria), Tecoma capensis (Cape honeysuckle), and Koelreuteria elegans (golden rain tree).

    • Even Pinnate - pinnate with an even number of leaflets; no end leaflet. Examples are Senna alata (candle bush) and Tamarindus indica (tamarind).

    • Bipinnate - leaflets are twice pinnate (the primary pinnae or leaflets are again divided into secondary leaflets), such as in Albizia julibrissin (mimosa), Delonix regia (royal poinciana), Melia azedarach (chinaberry), and Jacaranda spp. (jacaranda).

  1. Palmate - the leaflets are attached directly to the end of the petiole and extend outward much like fingers in a palm. Examples are Schefflera arboricola (Dwarf Schefflera) and Parthenocissus quinquefolia (Virginia creeper).

Leaf Arrangements on Stem

Alternate - one leaf at each node, as in Hibiscus rosa-sinensis (hibiscus), Brunfelsia pauciflora (yesterday-today-and-tomorrow), and Citrus spp. (citrus).

Opposite - two leaves at each node, always on opposite sides of the stem. Examples are Catharanthus roseus (vinca or periwinkle), Ixora coccinea (ixora), and Viburnum odoratissimum (sweet viburnum).

Whorled - more than two leaves at a node spaced around the stem, as in Nerium oleander (oleander) and Macadamia spp. (macadamia).

Leaf Attachments

Petiolate - petiole (leaf stalk) is present, examples are Hibiscus rosa-sinensis (hibiscus) and Quercus spp. (oaks).

Sessile - petiole (leaf stalk) is absent, leaf is attached directly to the main stem or branch, as in Podocarpus macrophyllus (Japanese yew) and Gloriosa superba (gloriosa lily).

Peltate - petiole attached to the lower surface of the leaf instead of at the base or margin, as in Tropaeolum majus (garden nasturtium).

Clasping - leaf partially encircles the stem, as in Calendula officinalis (calendula).

Sheathing - base of the leaf is wrapped around the stem like a grass leaf, as in Zea mays (corn) and Zingiber spp. (ginger).

Decurrent - leaf base extends downward to form a wing or ridge along the stem, as in Psidium guajava (guava).

Winged petiole - petiole has a leaf-like or membrane-like extension along its length, as in Citrus x paradisi (grapefruit).

Winged rachis - compound leaf stem with a membrane-like extension on both sides of the rachis, as in Rhus copallinum (winged sumac).

Stipule Types

Simple - stipules located on the sides of the petiole, as in Hibiscus rosa-sinensis (hibiscus).

Adnate - stipules that adhere to the sides of the petiole, as in Trifolium spp. (clover) and Rosa spp. (rose).

Leafy - green, leaf-like stipules that serve as foliage, as in Pisum sativum (pea) and Delonix regia (royal poinciana).

Other Leaf Types

Needle-shaped leaves - such as those in Pinus spp. (pines). Introduction

Needle-like leaves - margin of the leaf is so strongly rolled backward that the leaf appears tubular, such as in Rosmarinus officinalis (rosemary).

Awl-shaped and scale-like leaves - very reduced leaves, as in Platycladus orientalis (arbor vitae), Taxodium ascendens (pond cypress), and adult foliage of Juniperus virginiana (Eastern red cedar).

Leaf Textures

Succulent - juicy, fleshy, soft, and thickened in texture.

Scabrous - rough to the touch; texture of sandpaper.

Coriaceous - leather-like, tough.

Smooth (glabrous) - surface is not hairy, rough, pubescent, or scabrous.

Downy - covered with very short, weak, and soft hairs.

Pubescent - hairy.

Canescent - covered with gray or white soft hairs as in Leucophyllum frutescens (Texas sage).

Tomentose - covered with matted, woolly hairs.

Hirsute - pubescent with coarse, stiff hairs.

Hispid - rough with bristles, stiff hairs, or minute spines.

Chapter 6: Flower Branches, Clusters, and Inflorescences

Single Flower - one flower held at the end of an elongated stalk or branch of the main axis of the plant, as in tulip and Magnolia grandiflora (southern magnolia). [The peduncle is the stalk that bears a single flower or a cluster of flowers. The pedicel is the stalk of an individual flower in a cluster.]

Cluster - three or more flowers gathered closely together in simple or branched groups to increase their conspicuousness, such as in Pentas spp. (pentas), Ligustrum japonicum (ligustrum), Pyracantha coccinea (firethorn), Mangifera indica (mango), and Dianthus barbatus (Sweet William).

Inflorescence - general term for the arrangement of flowers on a plant. There is great diversity in this arrangement among different types of plants, but they generally remain characteristic for a particular type and may be useful in identifying species. There are two main types of inflorescences, racemose and cymose, and each is further subdivided.

  • Racemose Inflorescences - the axis of the inflorescence is indeterminate (continues to grow). The flowers are borne in the axes of the reduced leaves or bracts, with the oldest flowers at the base and the newest flowers near the growing tip.

  • Raceme - flowers on short pedicels of about equal length along the main axis, as in Antirrhinum majus (snapdragon) and Allamanda cathartica (allamanda).

  • Panicle - compound raceme (the branches have branches), with individual flowers replaced by simple racemes, as in Lagerstroemia indica (crapemyrtle) and Murraya paniculata (orange jessamine).

  • Spike - like a raceme, but flowers lack pedicels and are sessile or almost sessile. Examples are Acalypha wilkesiana (copperleaf) and Callistemon spp. (bottlebrush).

  • Spadix - type of spike; a fleshy axis bearing the sessile, generally fleshy flowers close together, commonly surrounded and partially enclosed by a spathe. Examples are Spathiphyllum (peace lily) and Zantedeschia and Anthurium spp. (anthurium).

  • Catkin - spike that normally produces only staminate or pistillate flowers (see next chapter), and at maturity falls away as a unit. Examples are Betula nigra (river birch) and Quercus spp. (oaks).

  • Corymb - pedicels of older flowers longer than those of younger flowers, which bring all of them to nearly the same level. Pedicels come from different points on the main peduncle, giving the inflorescence a rather flat-topped or convex look with the outside flowers opening first. Examples are Iberis spp. (candytuft) and Ixora coccinea (ixora).

  • Umbel - pedicels appear to arise from a common point (like an umbrella). This gives the inflorescence a knob-like look. The outer flowers open first. Examples are Anethum graveolens (dill) and Crinum spp. (crinum lily).

  • Head - similar to umbels, but sessile flowers are very close together. Heads may be globular or almost spherical as in Cephalanthus occidentalis (buttonbush) and Trifolium hybridum (clover). What popularly passes for a "flower" in the Compositae (Asteraceae) is really an inflorescence with many small, true flowers. For example, in Helianthus annuus (sunflower), ray flowers form a fringe of radiating irregular, asymmetrical flowers that often resemble petals (see chapter 8) on the edge of the head. Disk flowers cover the remainder of the head and are regular, symmetrical, and usually less showy. Heads may also have flowers that are all irregular with no differentiation into rays and disks.

  • Involucre – not an inflorescence per se; rather it is a (often conspicuous) cluster or whorl of bracts or leaves directly under a flower or a cluster of flowers. They are often found under umbels and heads. Examples are Helianthus annuus (sunflower) and the cups of acorns in Quercus spp. (oaks).

Cymose Inflorescences - Upward growth of the floral axis is stopped early by the development of a terminal flower. The first flower to open (the oldest) is at the tip; with younger flowers appearing lower down on the axis. The floral axis ceases to elongate after the first flower opens and is, therefore, a determinate inflorescence.

  • Cyme - one terminal flower and two or more side flowers coming from the end of the axis. Examples are Plumeria spp. (frangipani) and Solanum seaforthianum (Brazilian nightshade).

  • Scorpioid cyme - floral axis curves over, carrying the flowers along the top of the curve, as in Heliotropium spp. (heliotrope).

  • Fascicle - flowers are very closely crowded on almost the same plane (in a tight bundle or group), as in Dianthus barbatus (Sweet William).

Flower Positions

Terminal - flowers or clusters of flowers are carried on the ends of the axis or branches, as in Magnolia grandiflora (southern magnolia) and Nerium oleander (oleander).

Axillary - a flower or clusters of flowers arise at the junction of the stem and the leaf, as in Catharanthus roseus (periwinkle), Callicarpa americana (beautyberry), and Hibiscus rosa-sinensis (hibiscus).

Some plants, such as Ixora coccinea (ixora), have both terminal and axillary flowers.

Chapter 7: Flower Parts

A flower is the reproductive structure of some seed-bearing plants (angiosperms). The great variety of forms acts as a guide in separating flowering plants into major groups. Before we look at the different classifications of flowers, we must first learn the terms for the individual structures in the flower.

Accessory Organs

The following are known as accessory organs because they are not directly involved in pollination.

Calyx - the ring of sepals making up the outermost, leaf-like part of the flower. Sepals are commonly green, but may be almost any color and serve primarily as protection for the other floral parts.

Corolla - the inner set of leaf-like parts lying just within the calyx and composed of petals. Petals are generally white or brightly colored to attract pollinating insects to their nectar. They also serve as protection for the innermost organs.

Perianth - the outer floral parts, composed of the calyx and the corolla.

Tepal - used when a calyx and corolla are very similar and not easily distinguished, as in Lilium catesbaei (pine lily).

Receptacle or torus - the apex of the pedicel upon which the organs of a flower are developed.

Floral Bracts - modified leaves that can simulate petals and add a conspicuous part to otherwise inconspicuous flowers. Examples are the red bracts surrounding the small Euphorbia pulcherrima (poinsettia) flowers; the purple, red, or white leaves enclosing the small white flowers of Bougainvillea spp. (bougainvillea); or the white leaves of Cornus florida (flowering dogwood). Many plants have floral bracts that are not colorful, such as Fittonia albivenis (silver nerve plant).

Reproductive Organs

Reproductive organs are directly involved in pollination and fertilization; hence, their presence usually determines the survival of the species.

• Stamen - male reproductive organ consisting of an anther and a filament attached to the receptacle inside the corolla or to the corolla itself.

Filament - thin stalk that attaches the anther to the rest of the flower. Its attachment is called basal if it is at the lower end of the anther, as in Tulipa spp. (tulip); and versatile if it is lateral, near the center of the anther, as in Crinum spp. (crinum).

  • Anther - lobed, oblong, bag-like appendage at the top of the filament that produces the pollen grains that develop the male germ cells. Anthers are usually yellow and when young have from one to four cavities (cells) in which pollen grains arise. When mature, the anther usually contains two cavities from which the pollen grains are released by the formation of apical pores or longitudinal slits in the cavity wall.

  • Pollen Grains - usually appear as tiny specks barely visible to the unaided eye, but are produced in such quantity that they often form a layer of powder. Each grain is usually two-celled, spherical, ovoid, or disk-like in appearance, its surface marked with ridges, spines, and germ spores. Pollen grains, collectively known as pollen, are so characteristic of the different species that they are used for identification purposes.

In orchids and milkweeds pollen is in masses known as pollinia.

Stamens are called opposite when they are opposite to the petals, as in Vitis rotundifolia (muscadine grape) or Rhamnus caroliniana (Carolina buckthorn), and alternate when they alternate with the petals, as in Viola odorata (garden violet). The stamens are usually free or separate from each other, but in a few families they are united either by their filaments Hibiscus rosa-sinensis (hibiscus) and Lycopersicon esculentum (tomato) or by their anthers, as in Helianthus annuus (sunflower).

  • Pistil - female reproductive organs composed of a stigma, style, and ovary. Flowers may have just one simple pistil [as in Lathyrus odoratus (sweet pea)], or two, three, four, five, or more separate pistils as in Consolida spp. (larkspur). It (they) usually occurs in the very center of the flower and are often surrounded by the stamens, petals, and sepals. A carpel refers to either a simple pistil or one of the segments of a compound pistil. United carpels are found in Dietes iridioides (African iris) and Antirrhinum majus (snapdragon). Pistils are usually flask- or bottle-shaped.

  • Stigma - the tip of the pistil especially adapted to receive the pollen grains. The stigma may be expanded into a bulb or disk or divided into two or more slender parts. The stigma is often located atop a style.

  • Style - the elongated stalk or neck connecting the stigma with the ovary.

Ovary - enlarged, bulbous, basal part of the pistil that bears the ovules (the egg-containing units that, after fertilization, become the seeds) attached either to its central axis or to its inner wall. The tissue to which the ovules are attached is called the placenta. Each ovule usually contains one egg, the female gamete or sex cell. The ovule normally develops into a seed when fertilized. Generally there are two or more ovules per carpel. In some plants, only one may mature into a seed. The ovary normally develops into a fruit containing seeds. An example is the pod of Phaseolus lunatus (lima bean). A pistil is said to be compound when several or many carpels become united. Carpels are united so that a compound ovary often contains as many cavities as there are carpels. In some flowers a compound ovary becomes "one-celled" by the disappearance of the partitions between the different carpels as in Primula spp. (primrose). Union of carpels may be so complete that it includes the styles and stigmas as well as the ovaries.

Below are the different classifications of flowers according to the presence or absence of their parts:

  • Complete flowers are made up of calyx, corolla, stamens, and a pistil or pistils (the four "regular parts").

  • Incomplete flowers lack one or more of the four regular parts of a complete flower, as in the Fagaceae (oak family), Betulaceae (birch family) and Juglandaceae (walnut family).

  • Perfect flowers have both stamens and pistils, but not necessarily sepals or petals.

  • Imperfect flowers lack either stamens or pistils, and may or may not have sepals or petals.

  • Naked flowers are without petals (apetalous) or sepals (asepalous), as in Zantedeschia spp. (calla lily).

  • Apetalous flowers lack petals, as in Elaeagnus pungens (silverthorn), Hydrangea spp. and Cornus florida (flowering dogwood).

  • Staminate (male) flowers have a stamen or stamens, but no functional pistils.

  • Pistillate (female) flowers have a pistil or pistils, but no functional stamens.

Three terms are applied to plants based on their flowering characteristics:

  • Monoecious plants bear both staminate and pistillate flowers on the same plant, as in Quercus spp. (oak) and Zea mays (corn).

  • Dioecious plants bear staminate flowers on one plant and pistillate flowers on a different plant, hence the terms male and female plants. Ilex species (holly) and all cycads and many conifers are examples.

Polygamous plants bear staminate, pistillate, and hermaphroditic (bisexual - both sexes present and functional in the same flower) flowers on the same plant. An example is Acer rubrum (red maple).

Chapter 8: Flower Forms

Even a casual glance at the flowers in your garden will convince you of their diversity of form. This characteristic diversity in flower forms is a very important factor in plant identification. We have seen in Chapter 7 that flowers vary in the number of their floral parts, but they also vary in other ways relative to their parts:

1. Variations in the degree to which floral parts are united

Gamopetalous - petals united to form a tubular or rotate corolla with the united part known as the tube and the spreading or flat part known as the limb. These flowers take different forms as:

  • Funnel-form - the tube gradually widens upward and flares into the limb without any particular point of demarcation. Examples include Nerium oleander (oleander) and Ipomoea carnea (bush morning-glory).

  • Rotate - the tube is short and the limb is flat and circular. Lycopersicon esculentum (tomato), Sambucus canadensis (elderberry), and Vinca minor (creeping vinca) are examples.

  • Urn-shape (urceolate) - broad tube and slightly recurved, short limb, as in Vaccinium spp. (blueberry).

  • Salver-form - slender tube and an abruptly widened, flat limb. Phlox drummondii (annual phlox) and Catharanthus roseus (periwinkle) are examples.

  • Gamosepalous - flower with united sepals. Catharanthus roseus (periwinkle) and Hibiscus rosa-sinensis (hibiscus) are examples.

  • Polypetalous - petals of corolla composed of separate parts. Magnolia grandiflora (southern magnolia), Camellia japonica (camellia), and Rosa spp. (rose) are examples.

  • Polysepalous - sepals of calyx composed of separate parts. Magnolia grandiflora (southern magnolia) and Rosa spp. (rose) are examples.

2. Variations in placement of floral parts on the receptacle

  • Hypogynous (hi-poj'i-nus) - sepals, petals, and stamens are attached to a convex or conical receptacle at the base of the ovary. Sepals are arranged in the outermost or lowest layer, followed by petals and stamens, with carpels or ovary innermost. The ovary is called superior and the perianth is inferior or hypogynous. Lycopersicon esculentum (tomato) is an example.

  • Perigynous (pe-rij'i-nus) - sepals, petals, and sometimes stamens borne on the edge or margin of the receptacle so that they appear to form a cup around the pistil. Prunus persica (peach) is an example.

  • Epigynous (e-pij'i-nus) - sepals, petals, and stamens appear to arise from the top of the ovary. The concave receptacle not only surrounds the ovary, but is fused with it. In this case, the ovary is called inferior and the perianth is called superior or epigynous. Malus pumila (apple) is an example.

3. Variations in the number of subdivisions of each of the four regular parts

The number of sepals and petals is three (or multiples of three), as in monocots, four or five of each in the dicots, and reduced to none in some plants.

There is a large and indefinite number of stamens in many flower types, but in some there is a definite number, often the same as or twice the number of petals, or even further reduced to one or two.

Some flowers have a large number of separate pistils, but in others they are more or less united to form a compound pistil, and in many there is just one simple pistil.

4. Variations in the symmetry of flower forms

  • Regular or Actinomorphic (ak'ti-no-mor'fik) - floral parts, especially the corolla, are arranged symmetrically so that when quartered all sections are equal. Rosa spp. (rose), Camellia japonica (camellia), and Ipomoea carnea (bush morning-glory) are examples.

  • Irregular or Zygomorphic (zi'go-mor'fik) - floral parts are not arranged symmetrically, and when divided horizontally the two parts are unequal and dissimilar. There are three types of irregular flowers:

  • Papilionaceous (Peas or beans) - five petals arranged in distinct ways: Lathyrus odoratus (sweet pea) and Lupinus spp. (lupine) are examples. The three petal arrangements are as folllows:

  • Standard or Banner - large petal in the uppermost part or back of the flower.

  • Keel - two usually narrow and elongated petals in front of and usually below the standard.

  • Wings - two petals placed to the right and left of the keel and more or less clasping the keel.

  • Labiate (Mints) - tube of corolla usually deeply split into two irregular lobes, the upper lobe erect and made up of two petals, and the lower lobe spreading or open and composed of three petals. Bilabiate means two-lipped or double-lipped corolla. Salvia spp. (salvias) and Antirrhinum majus (snapdragon) are examples.

  • Orchidaceous (Orchids) - three sepals and three petals, with one petal, usually the lower one, modified to form a distinctive lip. Stamens are reduced and united with the pistil to form the column. Cattleya spp. (cattleya orchid) and Phalaenopsis spp. (moth orchid) are examples.

Chapter 9: Fruits and Seeds

Fruits are the ripened and seed-bearing ovaries of flowers. Fruits are nearly as varied in color, form, size, texture, and number as are flowers, making them valuable tools in plant identification.

Fruits

Botanists use the term "fruit" in a much broader way than does the layperson. Fruits are divided into two large categories: dry fruits and fleshy fruits.

Dry fruits are generally dull in color and have a very thin and dry ovary wall, so that the food is largely confined to the seeds. These may be further subdivided based on the number of seeds and whether the fruit remains closed at maturity (indehiscent) or opens naturally (dehiscent).

  • Achene - small, hard, indehiscent, one-cavitied, one-seeded fruit with a thin, almost inseparable wall, as in Helianthus annuus (sunflower).

  • Samara - indehiscent, one or two-seeded winged fruit, as in Acer rubrum (red maple).

  • Nuts - hard-shelled, usually one-seeded, indehiscent fruits, such as Juglans nigra (black walnut) or Carya illinoinensis (pecan).

  • Grain or Caryopsis - one-seeded, indehiscent fruit of most grasses, including the cereals. The enclosed seed is almost inseparable from the enveloping ovary wall. This fruit is little more than a seed for all practical purposes.

  • Capsule - dehiscent fruit composed of two or more carpels, generally with several or many seeds in each carpel, as in Gossypium spp. (cotton).

  • Silique - several-seeded fruit with two carpels that pull away from the central partition at maturity, as in Iberis odorata (candytuft) and Brassica spp. (mustard).

  • Silicle - a silique that is wider than long, such as in Lepidium virginicum (peppergrass).

  • Legume - pod formed from a simple pistil, dehiscent along both sides, as seen in Pisum sativum (pea) and Senna alata (candle bush).

  • Follicle - several-seeded fruit formed from a single carpel and splitting open along one side only. There may be two or more follicles produced by each flower, as in Mandevilla splendens (pink allamanda) and Asclepias spp. (milkweed).

  • Fleshy Fruits are usually juicy and brightly colored to make them more noticeable to the animals that eat and disperse them. All fleshy fruits are indehiscent, and considerable fleshy tissue is developed as the ovary changes into the fruit.

  • Drupe - "stone fruit," a simple fruit produced from a single carpel, usually one-seeded, with an outer fleshy layer of tissue called the pericarp and an inner, heavy stony layer called the endocarp. Examples are Prunus persica (peach), Cocos nucifera (coconut), Mangifera indica (mango), and Olea europaea (olive).

  • Berry - one or more carpels developed within a thin covering, very fleshy within, with the seeds embedded in the common flesh of a single ovary, such as Lycopersicon esculentum (tomato), Vaccinium spp. (blueberry), or Psidium guajava (guava).

  • Pepo - berry-like fruit of large size, with a tough or very firm and hard outer wall (rind) that is developed from the receptacle, such as Citrullus lanatus (watermelon), Cucumis sativus (cucumber), and Cucurbita spp. (squash).

  • Hesperidium - berry-like fruit of Citrus spp. (citrus) with a thick rind with numerous oil glands, and an interior fleshy part composed of wedge-shaped compartments, with or without seeds.

  • Pome - fruit developed largely from the receptacle that surrounds the carpels or inedible core parts, as in Malus spp. (apple) and Pyrus pyrifolia (sand pear).

  • Aggregate - fleshy fruit developed from the ovaries of a single flower, which becomes enlarged and bears many simple, true fruits as in Fragaria x ananassa (strawberry).

Multiple - fruits derived from many closely clustered flowers, such as in Morus spp. (mulberry) and Ananas comosus (pineapple). Seeds

Seeds consist of an outer coat or wall, which is usually very tough, hard, or woody, within which are cotyledons and the embryo. Seeds normally have just one embryo, but sometimes have more than one, as Citrus spp. (citrus) and Mangifera indica (mango), which results in two or more new plants growing from one seed. Seeds are developed as a result of the fertilization of the egg in the ovule of the ovary of a flower. Typically, seeds are oval or globular and range in size from dust-like orchid seeds to the large seed of the Persea americana (avocado), with some plants bearing seeds of even greater size such as Cocos nucifera (coconut). Seeds vary greatly in color, texture, longevity, and methods of dispersal. Some of the modifications of seeds that aid in dispersal are coverings of spines, hooks, bristles, cotton, or plumes, or having wings and arils. They also vary in the types and abundance of food they contain. Gymnosperms produce seeds but not true fruits since they have no ovary; such seeds are said to be naked and are borne on the inside of the scales or cones, but in plants such as Juniperus spp. (junipers) and Podocarpus spp. (podocarpus) they are embedded in a fleshy fruit-like organ, known as an aril.

Acknowledgements

This handbook was originally published in 1965 by the Florida Department of Agriculture and Consumer Services and the Florida Federation of Garden Clubs, Inc. The original text was by Nancy A. Knox and Ethel McSwiney.

The editors gratefully acknowledge the following University of Florida faculty for their assistance in reviewing the original IFAS publication: Dr. Robert J. Black, emeritus associate professor, Urban Horticulturist; Dr. David Hall, former associate n Natural Sciences, Botanist; and Dr. Bijan Dehgan, emeritus professor, Woody Ornamentals. Appreciation is also extended to Dr. Nancy Coile, botanist, Florida Department of Agriculture and Consumer Services, Gainesville, FL.

Footnotes

1.

This document is SSENH901, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date January 1962. Revised January 1999 and June 2013. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Sydney Park Brown, associate professor and consumer horticulture Extension specialist, Environmental Horticulture Department, GCREC-Plant City Campus; Kathleen C. Ruppert, Extension scientist, Agricultural and Biological Engineering Department; UF/IFAS Extension, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.