Family Picramniaceae

Picramniaceae (Engl.) Fernando & Quinn

~ Simaroubaceae

Habit and leaf form. Trees, or shrubs; non-laticiferous and without coloured juice. Plants non-succulent. Leaves alternate; petiolate; non-sheathing; not gland-dotted; without marked odour; compound; pinnate. Lamina pinnately veined; cross-venulate. Leaves exstipulate.

Leaf anatomy. Extra-floral nectaries present (abaxially on the lamina). Abaxial epidermis papillose, or not papillose. Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface (abaxial); anomocytic. Hairs present; eglandular and glandular.

Adaxial hypodermis absent. Lamina dorsiventral. The mesophyll without etherial oil cells (?); not containing mucilage cells; with sclerencymatous idioblasts, or without sclerenchymatous idioblasts; containing calcium oxalate crystals. The mesophyll crystals druses and solitary-prismatic (and styloids in Alvaradoa).

Stem anatomy. Cork cambium present; initially superficial. Secondary thickening developing from a conventional cambial ring. Xylem with fibre tracheids. Vessel end-walls simple.

Reproductive type, pollination. Fertile flowers functionally male, or functionally female. Plants dioecious. Female flowers with staminodes, or without staminodes. Gynoecium of male flowers pistillodial, or vestigial, or absent.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in panicles. Inflorescences terminal, or axillary, or cauliflorous. Flowers minute, or small; regular; 3–5(–6) merous. Floral receptacle with neither androphore nor gynophore. Free hypanthium absent.

Perianth with distinct calyx and corolla, or sepaline (male flowers sometimes lacking petals); 3–10(–12); 1 whorled, or 2 whorled; isomerous (when petals lacking), or anisomerous. Calyx 3–5(–6); 1 whorled; gamosepalous. Calyx lobes markedly longer than the tube. Calyx regular; imbricate, or valvate. Corolla when present, 3–5(–6) (sometimes absent from male flowers, reduced in female flowers); 1 whorled; imbricate; regular.

Androecium in male flowers, 3–5(–6). Androecial members free of the perianth; free of one another; 1 whorled. Androecium of male flowers exclusively of fertile stamens. Stamens 3–5(–6); isomerous with the perianth; alternisepalous; opposite the corolla members. Anthers versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with more than one middle layer (2 or 3). Pollen grains aperturate; 3 aperturate; colporate; 2-celled.

Gynoecium 2–3 carpelled. Carpels reduced in number relative to the perianth, or isomerous with the perianth. The pistil 1–3 celled. Gynoecium syncarpous; synovarious, or synstylovarious, or eu-syncarpous (?); superior. Ovary 1–3 locular. Gynoecium non-stylate to stylate. Styles shorter than the ovary. Placentation in Picramnia, axile to apical, or basal to axile (Alvaradoa). Ovules in the single cavity when unilocular, 2; 2 per locule; pendulous (when apical), or ascending (when basal); apotropous (Alvaradoa), or epitropous (Picramnia); hemianatropous, or anatropous (?); bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped. Hypostase present. Endosperm formation nuclear. Endosperm haustoria present; chalazal. Embryogeny onagrad.

Fruit fleshy, or non-fleshy; indehiscent; a berry (Picramnia), or capsular-indehiscent and a samara (Alvaradoa). Seeds non-endospermic. Cotyledons 2. Embryo straight, or curved (?).

Physiology, biochemistry. Arthroquinones detected (Alvaradoa, Picramnia); polyacetate derived.

Geography, cytology. Neotropical. Central and tropical America, West Indies.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Rutales. Cronquist’s Subclass Rosidae; Sapindales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Picramniales.

Species about 50. Genera 2; Alvaradoa, Picramnia.

Fernando and Quinn (1995). Note that satisfactory representation of recent notions on the proper dispositions of genera previously referred to Simaroubaceae will necessitate thorough overhaul of the descriptions presented in this package (cf. Irvingiaceae, Kirkiaceae, Simaroubaceae, Surianaceae, Stylobasiaceae). It is very easy to publish taxonomic realignments (with or without ‘diagnostic circumscriptions’), but harder to attend to the practical requirement for fully workable comparative descriptions.