| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Gyrostemonaceae Endl.

Habit and leaf form. Trees, or shrubs (or undershrubs). Xerophytic. Leaves small, or medium-sized; alternate; spiral; fleshy (often), or ‘herbaceous’ to leathery; petiolate to sessile; non-sheathing; simple; epulvinate. Lamina entire; linear, or lanceolate, or oblanceolate, or oblanceolate, or ovate; one-veined, or pinnately veined. Leaves stipulate (the stipules minute), or exstipulate; leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral, or bifacial, or centric. Mucilaginous epidermis commonly present. Stomata mainly confined to one surface, or on both surfaces; anomocytic. Lamina without secretory cavities. The mesophyll seemingly without crystals.

Axial (stem, wood) anatomy. Secretory cavities absent. Primary vascular tissues collateral. Internal phloem absent. Secondary thickening developing from a conventional cambial ring (with no anomalous structure recorded).

The vessel end-walls simple. The axial xylem with fibre tracheids (rare, but recorded in Gyrostemon), or without fibre tracheids; usually with libriform fibres. ‘Included’ phloem absent. The wood partially storied (VPI).

Reproductive type, pollination. Fertile flowers functionally male, or functionally female, or functionally male and functionally female. Unisexual flowers present. Plants dioecious (mostly), or monoecious.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in racemes, or in spikes. The ultimate inflorescence units racemose. Inflorescences racemose or spicate. Flowers bracteolate; small; regular; cyclic.

Perianth sepaline; when segments detectable, 4–5; joined (discoid or cupular, entire or more or less lobed); 1 whorled. Calyx when lobed, 4, or 5; 1 whorled; gamosepalous; entire, or lobulate, or blunt-lobed; regular; persistent.

Androecium 6–100 (i.e., to ‘many’, arising from the edge of the flat or convex receptacle). Androecial members when in more than one cycle, maturing centripetally; free of the perianth; all equal; free of one another; 1–5 whorled. Androecium exclusively of fertile stamens. Stamens 6–100 (to ‘many’); commonly polystemonous; filantherous (shortly), or with sessile anthers. Anthers dehiscing via longitudinal slits; introrse. Pollen grains aperturate; 3 aperturate; colpate, or colporate (?).

Gynoecium (2–)5–100 carpelled (i.e. to ‘many’). The pistil when syncarpous, (2–)5–25 celled. Gynoecium apocarpous to syncarpous; semicarpous to synovarious (the carpels adnate to the central column, forming a compound ovary); superior. Carpel non-stylate to stylate; apically stigmatic; if considered apocarpous, 1 ovuled. Placentation marginal. Ovary if viewed as syncarpous, (2–)5–25 locular (i.e., with as many locules as carpels). Gynoecium stylate, or non-stylate. Styles when present, (2–)5–25 (but very short); apical. Stigmas (2–)5–25 (the ring of stigmas forming a corona). Placentation axile. Ovules 1 per locule; apotropous; arillate; anatropous.

Fruit fleshy (often, at first), or non-fleshy (finally); interpretable as an aggregate (if seen as resulting from more or less ‘free’ carpels), or not an aggregate. The fruiting carpels coalescing into a secondary syncarp to not coalescing. Fruit a schizocarp (the carpels separating from the central column), or dehiscent and a schizocarp. Mericarps 2–25; comprising follicles, or comprising ‘legumes’ (the carpels dehiscing dorsally, ventrally or both). Seeds copiously endospermic. Endosperm oily. Embryo well differentiated. Cotyledons 2; flat. Embryo curved.

Physiology, phytochemistry. Mustard-oils present. Cyanogenic, or not cyanogenic. Iridoids not detected. Betalains absent (where sought). Proanthocyanidins absent. Ellagic acid absent. Aluminium accumulation not found. Sieve-tube plastids S-type.

Geography, cytology. Temperate to tropical. Australia. X = 14, 15.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Violiflorae; Capparales. Cronquist’s Subclass Dilleniidae; Batales. APG III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Brassicales.

Species 16. Genera 5; Codonocarpus, Cypselocarpus, (Didymotheca), Gyrostemon, Tersonia, Walteranthus.

Illustrations. • Gyrostemon thesioides (as Didymotheca): Hooker, Fl. Tasmaniae (1860). • Cypselocarpus haloragoides: Hook. Ic. Pl. 31 (1915). • Codonocarpus cotinifolius (Hutchinson). • Gyrostemon (carpel and fruit). • Gyrostemon ramulosus: Dict. Sci. Nat. 60, 1830 (BHL). • Gyrostemon ramulosus: Baiilon, Histoire des plantes 4 (1875).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or 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). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 8th June 2026. delta-intkey.com’.

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