I. SYNONYMS: dicots

II. NUMBER: > 200,000 extant species known.

III. CHARACTERISTICS OF THE CLASS

• A. Structure
  • Habit: Variable; these plants have an active cambium and range from herbaceous to woody. The dicots are seed plants which bear flowers and fruits. The embryos are dicotyledonous.
  • Flowers: The floral parts tend to be in sets of 5 or 4.
  • Pollen: Pollen walls are variable, but they usually have 3 apertures (although they range from 0-3). The microgametophyte has no prothallial cells or stalk cells and contains only 2 nonflagellate sperms and a tube cell.
  • Seeds: Ovules borne in a fruit (matured ovulary). Thus pollen tube must grow to the micropyle. The megagametophyte is greatly reduced, often of only 7 cells. Double fertilization produces the embryo and the endosperm. The embryo is dicotyledonous.
  • Stems: Eustelic, dicots have strong secondary growth. Xylem contains vessels.
  • Leaves: Usually net-veined blade with a petiole.
  • Roots: Protostelic (often actinostelic), with vessels.

• B. Ecology: Very abundant, the dicots have exploited almost every terrestrial and aquatic (not marine) habitat on this planet. Their fossil history dates back to the lower Cretaceous period.

SUBCLASS MAGNOLIIDAE

The flowers have tepals of variable number (sometimes they are differentiated into sepals and petals). The stamens develop centripetally with monosulcate pollen. Pistils are free (apocarpous) with bitegmatic ovules. Mature seeds have endosperm. This subclass has 8 orders (I give only 3 here).

• ORDER MAGNOLIALES
  • Trees, shrubs or vines. No vessels. Leaves simple with stipules. Perianth of free tepals. Stamens many and petaloid. Fruits usually follicles. This order contains 10 families, of which Magnoliaceae is the representative family.
  • Magnolia, Michelia, Manglietia, Talauma, Liriodendron.

• ORDER RANNUNCULALES
  • Herbs, vines, shrubs. Simple vessels. Leaves usually alternate, simple or compound; stipules either inconspicuous or absent. Flowers variable but hypogynous; usually with distinct sepals and petals. Stamens usually many; pollen with 3 apertures. Fruits variable: follicles, achenes, berries. This order contains 8 families, of which Rannunculaceae is the representative family.
  • Aconitum, Delphinium, Actaea, Aquilegia, Caltha, Coptis, Helleborus, Isopyrum, Anemone, Barneoudia, Hepatica, Adonis, Myosurus, Rannunculus, Thalictrum, Clematis, Clematopsis..

• ORDER PAPAVARALES
  • Herbs or shrubs. Simple vessels. Plants with milky latex. Leaves alternate or often in a basal rosette, usually compound or dissected; no stipules. Flowers usually large and showy, perfect, and hypogynous. Many stamens; pollen usually triaperturate. Fruits usually capsules which open by pores. This order contains 2 families, of which Papaveraceae is the representative family.
  • Papaver, Eschscholzia, Sanguinaria, Argemone, Chelodium.

SUBCLASS HAMAMELIDAE

Usually woody trees or shrubs. Reduced, often imperfect flowers grouped in catkins. Perianth usually absent. The mature fruit has a single seed, with or without endosperm. This subclass has 11 orders (I give only 3 here).

• ORDER URTICALES
  • Trees, shrubs, vines or herbs. Vessels simple. Leaves usually alternate; compound or simple; usually stipulate. Usually with sepals (4-5) and an equal number of stamens. Ovulary epigynous or hypogynous, usually with a single locule. Fruits variable but usually achenes or nuts. This order has 6 families, of which Moraceae is the representative family. Often this family is separated into the Cannabanaceae and the Moraceae. I have separated the groups of genera respectively.
  • Cannabis, Humulus.
  • Morus, Maclura, Broussonetia, Ficus, Artocarpus.

• ORDER JUGLANDALES
  • Aromatic trees or shrubs. Leaves alternate and usually pinnately compound. Flowers imperfect; sepals 4, stamens 3 to many. Gynoecium of 2 united carpels. Fruit often a drupe-like nut; embryo with little or no endosperm and oily. This order has 2 families, of which the Juglandaceae is the representative family.
  • Carya, Juglans.

• ORDER FAGALES
  • Trees or shrubs. Leaves alternate, simple and pinnately veined. Flowers small and imperfect. Often the staminate flowers are in catkins. Pistillate flowers subtended by an involucre of many bracts. Fruit a nut, samara or drupe. Seed with no endosperm. This order has 3 families, of which the Fagaceae is the representative family.
  • Fagus, Nothofagus, Lithocarpus, Castaniopsis, Castanea, Chrysolepis, Quercus, Trigonobalanus.

SUBCLASS CARYOPHYLLIDAE

The perianth is complex and diverse. Stamens mature centrifugally and produce trinucleate pollen. The embryos are surrounded by a perisperm. This subclass has 3 orders (I present only 1 order here).

• ORDER CARYOPHYLLALES
  • Herbs or shrubs with anomalous secondary growth. Vessels simple. Leaves alternate, opposite or whorled; simple, entire and often reduced to a spine. Flowers usually perfect, stamens usually numerous (generally 2X as many as there are perianth segments). Fruit variable, embryo large. This order has 12 families, of which the Cactaceae is the representative family.
  • Pereskia, Maihuenia, Opuntia, Pereskiopsis, Cereus, Echinocactus, Mammillaria, Gymnocalycium, Ferocactus, Lophophora, Astrophytum, Rhipsalis, Zygocactus, Epiphyllum.

SUBCLASS DILLENIIDAE

Many woody species. Stamens mature centrifugally and bear pollen with 2 nuclei. This subclass contains 13 orders (I present 5 orders here).

• ORDER MALVALES
  • Trees, herbs or shrubs. Vessels with simple perforations. Leaves usually alternate and palmately veined; stipules present. Flowers hypogynous and perfect. Often stamen filaments fused into a tube. Gynoecium usually of 5 fused pistils. Fruit usually capsular. Endosperm variable (none to much). This order has 12 families, of which the Malvaceae is the representative family.
  • Gossypium, Malva, Hibiscus, Sida, Malvastrum, Sidalcea, Kosteletzkya, Abutilon.

• ORDER VIOLALES
  • Trees, shrubs or herbs. Vessels with simple perforations. Leaves variable; alternate or opposite; usually simple; with or without stipules. Flowers with 4-5 sepals and 4-5 petals; perfect or imperfect. Stamens 5-many. Gynoecium often of 3 fused pistils. Fruit variable; dry or fleshy; dehiscent or indehiscent. This order has 24 families, of which the Violaceae and the Cucurbitaceae are representative families.
  • Violaceae: Anchaeta, Hybanthus, Rhinorea, Viola.
  • Cucurbitaceae: Citrullus, Ecballium, Lagenaria, Luffa, Momordica, Echinocystis, Cyclanthera, Sicyos, Cucurbita, Cayponia, Melothria, Cucumis, Pepo, Fevillea.

• ORDER SALICALES
  • Trees or shrubs. Vessels with simple perforations. Leaves alternate, simple, and stipulate. Flowers very reduced (no corolla and a reduced calyx), imperfect and borne in unisexual catkins. Seeds tiny and dispersed by means of seed hairs. No endosperm. This order contains the single family, Salicaceae.
  • Salix, Populus, Chosenia.

• ORDER CAPPARALES
  • Usually herbs but can be trees or shrubs. Vessels with simple perforations. Leaves usually alternate; simple, compound or dissected; with or without stipules. Flowers usually in terminal racemes and perfect. Perianth segments distinct and usually in 4’s. Stamens 4-many. Fruit usually a special capsule. This order contains 5 families, of which the Brassicaceae (Cruciferae) is the representative family.
  • Alyssum, Arabus, Amoracia, Barbarea, Capsella, Cardimine, Dentaria, Draba, Erysimum, Iberis, Isatis, Lepidium, Lunaria, Nasturtium, Brassica, Raphanus.

• ORDER ERICALES
  • Shrubs or small trees. Vessels with sclariform perforations. Leaves usually alternate, small, firm and perennial; no stipules. Flowers perfect and usually in racemes. Perianth segments usually in 5’s. Stamens 5-10. Fruit usually capsular. This order contains 8 families, of which the Ericaceae is the representative family. I have arranged the following genera into their respective subfamilies.
  • Arbutus, Arctostaphylos, Befaria, Calluna, Cassandra, Cassiope, Elliottia, Epigaea, Erica, Gaultheria, Kalmia, Ledum, Leiophyllum, Leucothoe, Lyonia, Menziesia, Oxydendrum, Phyllodoce, Pieris, Rhododendron, Zenobia.
  • Gaylussacia, Vaccinum.

SUBCLASS ROSIDAE

The flowers have numerous stamens which mature centripetally. Usually, the corollas are polypetalous. This subclass has 18 orders (I present 5 orders here).

• ORDER ROSALES
  • Woody or herbaceous. Leaves variable; alternate or opposite; simple or compound; with or without stipules. Stamens numerous. Gynoecium variable; apocarpous or syncarpous. Fruit variable. This order contains 24 families, of which the Rosaceae is the representative family. I have arranged the following families into their respective subfamilies.
  • Spieaea, Quillaja, Holodiscus.
  • Pyrus, Malus, Sorbus.
  • Adenostoma, Agrimonia, Alchemilla, Dryas, Frageria, Geum, Kerria, Rhodotypos, Rosa, Rubus, Potentilla.
  • Prunus.

• ORDER FABALES
  • Trees, shrubs, herbs or vines; very often with root nodules. Vessels simple. Leaves usually alternate and pinnately compound; stipulate. Flowers mostly in racemes, corymbs, spikes or heads. Strongly zygomorphic; 5 sepals; 5 petals. Gynoecium usually a single carpel. Fruit usually dry and dehiscent (a legume). Embryo large and no endosperm. This order contains 3 families, of which the Fabaceae (Leguminosae) is the representative family. I have arranged the following genera into their respective subfamilies.
  • Acacia, Albizzia, Mimosa, Prosopis, Schrankia.
  • Bauhinia, Cassia, Cercis, Gledistis, Gymnocladus.
  • Cladrastis, Sophora, Baptisia, Crotalaria, Lupinus, Medicago, Melilotus, Trifolium, Lotus, Astragalus, Oxytropis, Robinia, Tephrosia, Dalea, Psoralea, Indigofera, Arachis, Desmodium, Lespedeza, Dlabergia, Lathyrus, Lens, Faba, Pisum, Vicia, Glycine, Phaseolus, Pueraria, Rhynchosia, Vigna.

• ORDER EUPHORBIALES
  • Usually woody; often with latex. Leaves usually simple; with or without stipules. Flowers hypogynous, unisexual; perianth absent or reduced. Carpels united with as many styles as carpels. Fruit often a capsular schizocarp; seed with oily endosperm. This order contains 4 families, of which the Euphorbiaceae is the representative family.
  • Acalypha, Codiaeum, Croton, Euphorbia, Hevea, Jatropha, Manihot, Pedilanthus, Ricinus, Sapium, Tragia.

• ORDER SAPINDALES
  • Usually woody; often producing resinous compounds. Leaves variable; alternate, opposite or whorled; simple or compound; usually lobed; stipules absent or reduced. Flowers perfect or imperfect; usually actinomorphic; 4 or 5 merous. Gynoecium of 2-5 carpels united; 1-2 ovules per locule. Fruit variable; seeds with or without endosperm. This order contains 15 families, of which the Rutaceae and Aceraceae are representative families.
  • Aceraceae: Acer, Dipteronia.
  • Rutaceae: Citrus, Xanthoxylum, Ruta, Ptelea, Murraya, Fortunella.

• ORDER APIALES
  • Woody or herbaceous. Vessels with simple, sclariform perforations. Leaves usually alternate; usually compound or dissected. Petiole usually broad and sheathing. Flowers small and in umbles or compound umbels; usually perfect. Usually 5-merous. Gynoecium2-5 carpels fused; inferior; styles as many as carpels. Fruit a drupe, berry or schizocarp. Seeds small with abundant endosperm. This order contains 2 families, of which Apiaceae (Umbelliferae) is the representative family. The following genera are arranged into their respective subfamilies.
  • Azorella, Hydrocotyle, Bowlesia.
  • Eryngium, Sanicula, Lagoecia.
  • Echinophora, Anthriscus, Chaerophyllum, Torilis, Coriandrum, Conium, Apium, Bupleurum, Carum, Foeniculum, Ligusticum,Angelica, Ferula, Pastinacea, Laserpitium, Thapsia, Daucus.

SUBCLASS ASTERIDAE

Woody or herbaceous. Usually vessels with simple perforations. Corolla usually sympetalous; stamens usually attached to the corolla tube. This subclass contains 11 orders (I present 3 orders here).

• ORDER SOLANALES
  • Usually herbs, shrubs or vines. Leaves usually alternate; simple to compound; no stipules. Flowers perfect, actinomorphic, and 5-merous; the 5 stamens attached to the corolla tube. Gynoecium usually with 2 carpels. Fruit a capsule or a berry. Endosperm present to absent. This order contains 8 families, of which Solanaceae is the representative family.
  • Atropa, Browallia, Capsicum, Chamaesaracha, Datura, Hyoscyamus, Lycium, Lycopersicon, Nicandra, Nicotiana, Petunia, Physalis, Salphichroa, Schizanthus, Solanum.

• ORDER LAMIALES
  • Herbs, shrubs or trees. Leaves variable but usually opposite and simple, no stipules. Flowers perfect with a 5-merous perianth, corolla fused and usually zygomorphic. Usually 5 stamens. Gynoecium usually of 2 carpels, each with 2 ovules. The fruit is formed by the carpels separating into 4 1-seeded nutlets. Endosperm usually lacking. This order contains 4 families, of which Lamiaceae (Labiatae) is the representative family.
  • Ajuga, Mentha, Thymus, Rosmarius, Salvia, Scutellaria, Lamium, Monarda, Coleus, Ocimum, Perlla, Prunella, Stachys, Teuchrium, Plectranthus, Origanum, Nepeta, Glechoma, Leonurus, Leonotis, Ballota.

• ORDER ASTERALES
  • Mostly herbs. Commonly store polysaccharide as inulin; some with latex in the plant. Leaves usually alternate and simple; no stipules. Inflorescence usually a head or compound heads. Flowers epigynous, sympetalous; usually perfect (some neutral or functionally staminate). Ray flowers zygomorphic and disc flowers actinomorphic (5-merous). Five stamens fused around the style. Fruit and achene, often with a persistent pappus at the top. This order contains a single large family, the Asteraceae Compositae). The following genera have been arranged according to the two subfamilies.
  • Ambrosia, Bidens, Borrichia, Coreopsis, Echinacea, Eclipta, Helenium, Helianthus, Iva, Parthenium, Rudbeckia, Silphium, Verbesina, Xanthium, Zinnia. Aphanostephus, Aster, Astranthium, Baccahris, Bellis, Bigelowia, Boltonia, Britonia, Chrysoma, Chrysopsis, Conyza, Erigeron, Euthamia, Grindelia, Gutierrezia, Haplopappus, Heterotheca, Solidago, Achillea, Anthemis, Artemisia, Chrysanthemum, Hymenopappus, Matricaria, Solvina, Tanacetum, Arctotis, Anaphalis, Antennaria, Evax, Facelis, Filago, Gnaphalium, Inula, Pluchea, Pterocaulon, Sachsia, Arnica, Cacalia, Emilia, Erechtites, Gynura, Petasites, Senecio, Tussilago, Calendula, Ageratum, Brikellia, Carphephorus, Eupatorium, Garberia, Hartwrightia, Kuhnia, Liatris, Mikania, Sclerolepis, Trilisa, Elephantopus, Stokesia, Vernonia, Arctium, Centaurea, Cirsium, Cnicus, Silybum, Chaptalia, Mutisia, Gerbera.
  • Cichorium, Crepis, Hieracium, Krigia, Lactuca, Prenanthes, Pyrrhopappus, Sonchus, Taraxacum, Tragopogon.