Hugoniaceae Arn.
~ Linaceae
Excluding Ctenolophonaceae
Habit and leaf form. Lianas. Climbing; scrambling (the lower inflorescence branches modified into hooks). Leaves alternate; simple. Lamina entire. Leaves stipulate. Stipules caducous.
Leaf anatomy. Mucilaginous epidermis present. Stomata present; paracytic.
Lamina dorsiventral. The mesophyll with sclerencymatous idioblasts.
Stem anatomy. Nodes tri-lacunar. Secondary thickening developing from a conventional cambial ring. Vessel end-walls scalariform and simple, or scalariform, or simple. Wood parenchyma apotracheal (confluent).
Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in spikes, or in panicles. Inflorescences terminal, or axillary. Flowers small to large; somewhat irregular, or very irregular. The floral irregularity involving the perianth (the calyx only), or involving the androecium. Flowers neither papilionaceous nor pseudo-papilionaceous; 5 merous. Free hypanthium absent. Hypogynous disk present; extrastaminal; of separate members (represented by 2–5 glands).
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous (the sepals commonly more or less unequal); imbricate. Corolla 5; 1 whorled; polypetalous; contorted; regular; deciduous (fugacious).
Androecium 10, or 15. Androecial members free of the perianth; usually markedly unequal; coherent (the filaments connate for much of their length, forming a tube); 1 adelphous. Androecium exclusively of fertile stamens, or including staminodes (? — the extrastaminal glands). Staminodes (the glands) 2–5; external to the fertile stamens. Stamens 10, or 15; diplostemonous, or triplostemonous; both alternating with and opposite the corolla members. Anthers dehiscing via longitudinal slits. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate.
Gynoecium 2–5 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 2–5 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary 2–5 locular (sometimes with the partitions not quite reaching the summit). Locules without ‘false septa’. Gynoecium stylate. Styles 1, or 2–5; free, or partially joined. Placentation axile to apical. Ovules 2 per locule; pendulous; epitropous (the micropyle directed upwards and outwards); with ventral raphe; with a placental obturator; anatropous; bitegmic; crassinucellate.
Fruit fleshy; indehiscent; a drupe. Seeds scantily endospermic, or non-endospermic. Embryo well differentiated. Cotyledons 2. Embryo slightly curved, or straight.
Physiology, biochemistry. Saponins/sapogenins present.
Geography, cytology. Paleotropical. Sub-tropical to tropical. Tropical Africa, Madagascar, Indomalaysia, New Caledonia. X = 12, 13.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Geraniales. Cronquist’s Subclass Rosidae; Linales. APG (1998) Eudicot; core Eudicot; Rosid; Eurosid I; Malpighiales. Species 40. Genera perhaps 5; Hugonia, plus Hebepetalum, Indorouchera, Philbornea, Roucheria.
Illustrations. • Technical details (Hugonia).
Cite this publication as: ‘L. Watson and M. J. Dallwitz (1992 onwards). The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 14th December 2000. http://biodiversity.uno.edu/delta/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), and Watson and Dallwitz (1991) should also be cited (see References).
