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L. Watson and M. J. Dallwitz

Stylidiaceae R. Br.

Including Candolleaceae Schönl.; excluding Donatiaceae.

Habit and leaf form. Herbs, or shrubs (or shrublets). ‘Normal’ plants, or switch-plants (occasionally); sometimes with the principal photosynthesizing function transferred to stems (e.g., the rush-like S. junceum). Leaves well developed (usually), or well developed and much reduced (commonly with basal leaves, and scales above), or absent (occasionally). Perennial; with a basal aggregation of leaves (often), or with terminal aggregations of leaves (often with cauline rosettes), or without conspicuous aggregations of leaves; rhizomatous, or tuberous. Self supporting (mostly), or climbing (rarely); when scandent, scrambling (Stylidium scandens, via leaf tips recurved into hooks). Helophytic (in bogs), or mesophytic to xerophytic. Leaves alternate (usually, conspicuously so), or whorled (Stylidium scandens); spiral; ‘herbaceous’, or leathery; imbricate; subsessile; sheathing; simple. Lamina entire; when present and well developed, linear (grasslike); parallel-veined; without cross-venules. Leaves exstipulate.

Leaf anatomy. The leaf lamina dorsiventral. Hydathodes present (occasionally), or absent. The mesophyll containing mucilage cells; without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Stylidium).

Axial (stem, wood) anatomy. Primary vascular tissues of the scape variously in a cylinder, without separate bundles, or comprising a ring of bundles, or comprising two or more rings of bundles, or consisting of scattered bundles; collateral, or bicollateral (often with bundles variously orientated). Internal phloem present, or absent. Secondary thickening absent, or developing from a conventional cambial ring (?).

The axial xylem with fibre tracheids; without libriform fibres (?). The wood partially storied (VI).

Reproductive type, pollination. Plants hermaphrodite, or monoecious, or polygamomonoecious, or dioecious (?). Pollination entomophilous; mechanism conspicuously specialized (in Stylidium the stylar column springs violently from one side when triggered so as to deposit pollen on a visiting insect, while in Levenhookia the column is immobile but the hooded labellum springs so as to cause shedding of pollen).

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes, or in racemes, or in spikes, or in corymbs. The ultimate inflorescence units cymose, or racemose. Inflorescences scapiflorous (often), or not scapiflorous; terminal. Flowers bracteate; small to medium-sized; very irregular; resupinate to not resupinate. The floral irregularity involving the perianth and involving the androecium, or involving the androecium (occasionally the corolla is almost regular). Flowers 5 merous; cyclic; pentacyclic. Floral receptacle developing an androphore (the peculiar ‘stylar column’, which bears the stigma and the anthers at its tip, sometimes being thus interpreted), or with neither androphore nor gynophore (i.e., if the column is interpreted as a gynostemium). Free hypanthium present.

Perianth with distinct calyx and corolla; (7–)10(–12); 2 whorled; isomerous (usually), or anisomerous. Calyx (2–)5(–7); 1 whorled; polysepalous, or gamosepalous; bilabiate (usually); imbricate; with the median member posterior. Corolla 5 (though often ostensibly only 4, with two pairs of conspicuous lobes); 1 whorled; appendiculate (in the throat, or the labellum appendaged), or not appendiculate; gamopetalous; imbricate (and resupinate or partly so); unequal but not bilabiate (the anterior member different from the others, forming a ‘labellum’, often much smaller and/or otherwise different from the rest), or regular; white, or pink, or purple.

Androecium 2. Androecial members free of the perianth; united with the gynoecium (seemingly forming an often irritable column with the style, the stigma and stamens borne at its tip); coherent; 1 adelphous (via the gynostemium); 1 whorled (posterior-lateral). Androecium exclusively of fertile stamens. Stamens 2(–3); reduced in number relative to the adjacent perianth. Anthers dehiscing via longitudinal slits; extrorse; tetrasporangiate. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer; of the ‘dicot’ type. Tapetum glandular. Pollen grains aperturate; 3–8 aperturate; colpate; 2-celled.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled, or 2 celled. Gynoecium syncarpous (but sometimes pseudomonomerous by abortion); eu-syncarpous; inferior. Ovary 2 locular (usually), or 1 locular (by abortion of the posterior locule). Gynoecium median. Epigynous disk present, or absent. Styles 1. Stigmas dry type; papillate; Group II type. Placentation when both locules fertile axile. Ovules in the single cavity when only one locule fertile 1, or 4; 15–50 per locule (‘many’); pendulous, or horizontal, or ascending; anatropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; persistent. Synergids elongated, hooked (and sometimes with filiform apparatus). Endosperm formation cellular. Endosperm haustoria present (aggressive); chalazal and micropylar. Embryogeny solanad.

Fruit fleshy to non-fleshy; dehiscent, or indehiscent (rarely); a capsule; 4–100 seeded (‘few to many’). Seeds endospermic. Endosperm oily. Seeds minute. Cotyledons 2.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Inulin recorded. Not cyanogenic. Alkaloids absent (3 species). Iridoids detected; ‘Route I’ type. Saponins/sapogenins present (rarely), or absent. Proanthocyanidins present (normal and seco). Flavonols present, or absent; kaempferol and quercetin. Ellagic acid absent (2 species of Stylidium). Aluminium accumulation not found.

Geography, cytology. Temperate to tropical. Southeast Asia, Malaysia, Australia, New Zealand, southernmost South America. N = 15, 18.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Asteridae; Campanulales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; campanulid; Order Asterales.

Species 150. Genera 5; Fostera, Levenhookia, Oreostylidium, Phyllachne, Stylidium.

General remarks. The anatomical component of this description, compiled from Metcalfe and Chalk, is hopelessly unsatisfactory.

Illustrations. • Technical details: Stylidium. • Stylidium adnatum: Bot. Reg. 914, 1825. • Stylidium brunonianum: Bot. Reg. 15, 1842. • Stylidium sp., cf. brunonianum: habitat (photo). • Stylidium fasciculatum: Bot. Reg. 1459, 1831. • Stylidium graminifolium: Bot. Reg. 90, 1815. • Stylidium laricifolium: Bot. Reg. 550, 1821. • Stylidium pilosum: Bot. Reg. 41, 1842. • Stylidium sp., cf. junceum: inflorescence detail (photo). • Stylidium sp.: inflorescence detail (photo).

The descriptions are offered for casual browsing only. We strongly advise against extracting comparative information from them. This is much more easily achieved using the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG).

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 2nd April 2015.’.