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The families of flowering plants.                                                                                                                                                                

Stackhousiaceae R. Br.

                        

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~Celastraceae

Habit and leaf form. Herbs. ‘Normal’ plants, or switch-plants. Leaves well developed, or much reduced. Plants succulent, or non-succulent. Annual, or perennial; perennials rhizomatous. Mesophytic, or xerophytic. Leaves alternate; spiral; ‘herbaceous’, or leathery, or fleshy, or membranous; petiolate to sessile; non-sheathing; simple; epulvinate. Lamina entire; linear, or lanceolate, or oblanceolate; one-veined, or pinnately veined. Leaves inconspicuously stipulate. Stipules interpetiolar; scaly (or terete); caducous (usually?), or persistent. Lamina margins entire.

Leaf anatomy. Stomata present; anomocytic.

Lamina dorsiventral, or isobilateral, or centric. The mesophyll without calcium oxalate crystals.

Stem anatomy. Secondary thickening developing from a conventional cambial ring (?). Xylem with fibre tracheids. Vessel end-walls simple.

Reproductive type, pollination. Unisexual flowersabsent. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, or in racemes, or in umbels. The ultimate inflorescence unit cymose, or racemose. Inflorescences racemes or cymes, rarely umbellate. Flowers bracteate; bracteolate (usually, with two bracteoles), or ebracteolate; fragrant (mostly?), or odourless; regular to somewhat irregular. The floral irregularity involving the androecium. Flowers 5 merous; cyclic; tetracyclic. Free hypanthium present. Hypogynous disk present (lining the floral tube).

Perianthwith distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous (on the hypanthium), or gamosepalous (towards the base above the hypanthium); regular, or unequal but not bilabiate; imbricate. Corolla 5; 1 whorled; polypetalous, or gamopetalous; imbricate; unequal but not bilabiate, or regular; white, or yellow, or pink, or purple. Petals clawed (the claws free, even when gamopetalous above).

Androecium 5. Androecial members free of the perianth; markedly unequal (usually three long, two short), or all equal (Macgregoria); free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members. Anthers dehiscing via longitudinal slits; tetrasporangiate; appendaged (Macgregoria), or unappendaged. The anther appendages apical. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer. Tapetum glandular. Pollen grains aperturate; 3 aperturate; colporate; 3-celled.

Gynoecium (2–)3(–5) carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil (2–)3(–5) celled. Gynoecium syncarpous; synovarious to eu-syncarpous; superior. Ovary (2–)3(–5) locular. Gynoecium stylate. Styles 1, or 2–5; free, or partially joined; attenuate from the ovary, or from a depression at the top of the ovary; apical.Stigmas 2–5. Placentation axile to basal. Ovules 1 per locule; ascending; apotropous; with ventral raphe; anatropous; bitegmic; tenuinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3 (sometimes multinucleate); proliferating (to form 10–15 cells), or not proliferating. Synergids pear-shaped. Hypostase present. Endosperm formation nuclear. Embryogeny asterad.

Fruit non-fleshy; a schizocarp. Mericarps (2–)3(–5); comprising nutlets, or samaroid. Fruit 2–5 seeded. Seeds endospermic. Endosperm oily. Cotyledons 2. Embryo straight.

Seedling.Germination phanerocotylar.

Physiology, biochemistry. Not cyanogenic. Iridoids not detected. Proanthocyanidins present. Aluminium accumulation not found.

Geography, cytology. Temperate to tropical. Malaysia, Australia, New Zealand. X = 9, 10, 15.

Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Santaliflorae; Celastrales. Cronquist’s Subclass Rosidae; Celastrales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Celastrales (as a synonym of Celastraceae).

Species 27. Genera 3; Macgregoria, Stackhousia, Tripterococcus.

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