Family Rhamnaceae
Rhamnaceae Juss.Including Camarandraceae Dulac, Cryptandraceae Barkley, Frangulaceae Lam. & DC., Gouaniaceae, Phylicaceae J.G. Agardh Habit and leaf form. Trees, shrubs, and lianas, or herbs (Crumenaria). ‘Normal’ plants, or switch-plants; often with the principal photosynthesizing function transferred to stems. Leaves well developed, or much reduced. Self supporting, or climbing; climbers tendril climbers, or scrambling. Leptocaul. Mesophytic, or xerophytic. Leaves alternate, or opposite; when alternate, spiral; ‘herbaceous’, or membranous, or modified into spines; petiolate to sessile; non-sheathing; simple. Lamina entire; one-veined, or pinnately veined, or palmately veined; cross-venulate. Leaves stipulate, or exstipulate. Stipules when present, intrapetiolar; free of one another; scaly, or spiny. Domatia occurring in the family (4 genera); manifested as pits, or pockets, or hair tufts. Leaf anatomy. Mucilaginous epidermis usually present. Stomata present; anomocytic (usually), or paracytic. Adaxial hypodermis present, or absent. Lamina dorsiventral (usually), or isobilateral to centric (occasionally); with secretory cavities, or without secretory cavities. Secretory cavities containing mucilage. The mesophyll commonly containing mucilage cells; containing calcium oxalate crystals. The mesophyll crystals druses, or solitary-prismatic (or acicular styloids, in Gouania). Minor leaf veins without phloem transfer cells (Ceanothus, Pomaderris). Stem anatomy. Secretory cavities present, or absent; with mucilage. Cork cambium present; initially superficial. Nodes tri-lacunar. Primary vascular tissue in a cylinder, without separate bundles. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones (often), or not stratified. ‘Included’ phloem absent. Xylem with libriform fibres; with vessels. Vessel end-walls simple. Vessels with vestured pits (rarely), or without vestured pits. Wood parenchyma predominantly paratracheal (in most species), or apotracheal (e.g. some Zizyphus spp.). Reproductive type, pollination. Plants hermaphrodite, or monoecious, or androdioecious, or polygamomonoecious (?). Pollination entomophilous. Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, in heads, in corymbs, and in panicles. The ultimate inflorescence unit cymose. Inflorescences terminal, or axillary; variously cymes, thyrses, corymbs, fascicles, even compound heads in Spyridium and Stenanthemum. Flowers small; regular; (4–)5 merous; cyclic; tetracyclic, or pentacyclic. Floral receptacle when free, markedly hollowed. Free hypanthium present (whether ovary superior or inferior). Hypogynous disk present (when stamens hypogynous). Perianth with distinct calyx and corolla, or sepaline (the corolla sometimes lacking); 5, or 8, or 10; 2 whorled (usually), or 1 whorled; isomerous. Calyx (4–)5; 1 whorled; polysepalous, or gamosepalous; regular; valvate. Corolla (4–)5 (often small); 1 whorled; polypetalous; induplicate valvate; regular. Petals clawed (often), or sessile. Androecium (4–)5. Androecial members free of the perianth (inserted at the mouth of the hypanthium), or adnate (then the filaments adnate to the corolla); free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens (4–)5; isomerous with the perianth; alternisepalous (and usually hooded by the petals, at least when young); opposite the corolla members. Anthers dorsifixed; versatile; dehiscing via longitudinal slits, or dehiscing by longitudinal valves; introrse. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Anther wall initially with more than one middle layer (2); of the ‘basic’ type. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; usually 3 aperturate; usually colporate; 2-celled (in Scutia and Zizyphus). Gynoecium (2–)5 carpelled. Carpels isomerous with the perianth, or reduced in number relative to the perianth. The pistil 1 celled, or (2–)3(–5) celled. Gynoecium syncarpous; synovarious to synstylovarious; superior to inferior. Ovary (2–)3(–5) locular, or 1 locular (by abortion). Epigynous disk usually present (when ovary inferior). Gynoecium stylate. Styles 1 (deeply cleft); apical. Stigmas (2–)5; dry type; papillate; Group II type. Placentation when unilocular, basal; when plurilocular, basal. Ovules in the single cavity when unilocular, 1; when 2–5 locular, 1(–2) per locule; funicled to sessile; ascending; when plurilocular, epitropous; with dorsal raphe; when paired, collateral; arillate, or non-arillate; anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type, or Allium-type. Antipodal cells formed; 3 (enlarging, sometimes becoming coenocytic); not proliferating. Synergids hooked (usually with filiform apparatus). Hypostase present, or absent. Endosperm formation nuclear. Embryogeny asterad, or solanad. Fruit fleshy, or non-fleshy; indehiscent, or a schizocarp. Mericarps when schizocarpic, 2–5. Fruit when non-schizocarpic, a drupe, or a nut; without fleshy investment. The drupes with separable pyrenes, or with one stone. Fruit sometimes elastically dehiscent. Dispersal unit the mericarp, or the fruit (the latter often specially adapted to wind carriage). Seeds endospermic (thinly), or non-endospermic. Endosperm ruminate (Reynosia), or not ruminate. Embryo well differentiated. Cotyledons 2. Embryo chlorophyllous (4/6); straight. Seedling. Germination phanerocotylar, or cryptocotylar. Physiology, biochemistry. Nitrogen-fixing root nodules present (with actinomycetes, in Ceanothus), or absent. Not cyanogenic. Alkaloids present (commonly), or absent. Iridoids not detected. Arthroquinones detected (4 genera); polyacetate derived. Proanthocyanidins present, or absent; when present, cyanidin, or cyanidin and delphinidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent (5 species, 3 genera). Arbutin absent. Saponins/sapogenins present, or absent. Aluminium accumulation not found. Sugars transported as sucrose (in four genera). C3. C3 physiology recorded directly in Ceanothus, Rhamnus. Anatomy non-C4 type (Ziziphus). Geography, cytology. Temperate to tropical. Cosmopolitan, except frigid regions. X = (9-)12/13(-23). Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Rhamnales. Cronquist’s Subclass Rosidae; Rhamnales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Rosales. Species 900. Genera about 50; Adolphia, Alphitonia, Alvimiantha, Ampelozizyphus, Auerodendron, Bathiorhamnus, Berchemia, Berchemiella, Blackallia, Ceanothus, Chaydaia, Colletia, Colubrina, Condalia, Crumenaria, Cryptandra, Discaria, Doerpfeldia, Emmenosperma, Gouania, Helinus, Hovenia, Karwinskia, Kentrothamnus, Krugiodendron, Lasiodiscus, Maesopsis, Nesiota, Noltea, Paliurus, Phylica, Pomaderris, Reissekia, Retanilla, Reynosia, Rhamnella, Rhamnus, Sageretia, Schistocarpaea, Scutia, Siegfriedia, Smythea, Spyridium, Talguenea, Trevoa, Trymalium, Ventilago, Ziziphus. Economic uses, etc. Edible drupes from Ziziphus spp. (jujube, Chinese date, ber or bor). Purgative (cascara sagrada) from Rhamnus purshiana. Illustrations. |
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