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The families of flowering plants

L. Watson and M.J. Dallwitz

Amaranthaceae Juss.

Including Deeringiaceae J.G. Agardh, Subscariosaceae Dulac; excluding Chenopodiaceae, Goetzeaceae

Habit and leaf form. Shrubs and herbs. Plants succulent (occasionally, if the halophytic Hemichroa is referred here rather than to Chenopodiaceae), or non-succulent (mostly); green and photosynthesizing. With a basal aggregation of leaves (occasionally, e.g. in Ptilotus), or without conspicuous aggregations of leaves (usually). Self supporting, or climbing (occasionally). Leaves alternate, or opposite; ‘herbaceous’ (mostly), or fleshy (perhaps only Hemichroa); sheathing, or non-sheathing; simple. Lamina entire; one-veined, or pinnately veined. Leaves exstipulate. Lamina margins entire. Domatia commonly occurring in the family.

General anatomy. Plants commonly with ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral (very rarely tending to isobilateral). Abaxial epidermis not papillose. Stomata on both surfaces (commonly), or mainly confined to one surface (usually more numerous abaxially); anomocytic, or anisocytic (? - subsidiary patterns not precisely specified by Solereder or Metcalfe and Chalk). Hairs present (of assorted types, see illustration; but only uniseriate trichomes that often form dense woolly or silky indumentum seem to predominate across the family); eglandular and glandular; mostly seemingly multicellular. Multicellular hairs branched and simple. Complex hairs present, or absent; sometimes stellate, or capitate. Adaxial hypodermis absent. The mesophyll containing crystals. The crystals mostly druses (and crystal sand, solitary types being rare; cf. Caryophyllaceae, differing from Nyctaginaceae in absence of raphides and styloids). Main veins embedded. Minor leaf veins without phloem transfer cells (Amaranthus, Celosia).

Axial (stem, wood) anatomy. Cork cambium present, or absent; initially superficial. Nodes unilacunar. Primary vascular tissues presumably comprising a ring of bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles present (commonly), or absent. Secondary thickening anomalous (nearly always), or developing from a conventional cambial ring (rarely?). The anomalous secondary thickening when present (i.e. usually) via concentric cambia (in secondary rings or arcs, the former giving rise to circles of collateral bundles, the latter resulting in their being irregularly distributed). Primary medullary rays wide.

The vessels small to medium. The vessel end-walls simple. The vessels without vestured pits; without spiral thickening. The axial xylem without fibre tracheids; with libriform fibres; without septate fibres. The fibres without spiral thickening. The parenchyma paratracheal. ‘Included’ phloem present (commonly, usually of the concentric type), or absent. The wood storied (Charpenteria, Iresine), or partially storied (?), or not storied (?).

Reproductive type, pollination. Plants hermaphrodite (usually), or monoecious, or andromonoecious, or gynomonoecious, or dioecious, or androdioecious, or polygamomonoecious (rarely).

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’ (usually with conspicuous, persistent bracts and bracteoles); when aggregated, in cymes, or in spikes, or in heads. The ultimate inflorescence units cymose. Inflorescences racemes of cymes; with involucral bracts (rarely), or without involucral bracts; pseudanthial, or not pseudanthial. Flowers bracteate; bracteolate; regular; cyclic; tricyclic. Free hypanthium absent (except, dubiously, in some Ptilotus species, where the androecial tube is adnate to the calyx). Hypogynous disk absent.

Perianth sepaline (dry and scarious); 3–5; sepaloid, or petaloid. Calyx 3–5; polysepalous, or gamosepalous (partially); regular; non-fleshy; persistent (dry, stiff and scarious); accrescent (e.g. some Ptilotus species), or non-accrescent; imbricate; when K 5, with the median member posterior.

Androecium (1–)2, or 5, or 6–10. Androecial members free of the perianth, or adnate (to the perianth or disk); markedly unequal (usually, by contrast with most Chenopodiaceae), or all equal (more or less, e.g. in some Ptilotus species); usually basally coherent (by contrast with most Chenopodiaceae); 1 adelphous (the filaments usually connate for all or part of their length into a membranous tube); 1 whorled. Androecium exclusively of fertile stamens, or including staminodes (commonly, by contrast with most Chenopodiaceae — some androecial members may lack anthers, also there are often ‘petaloid enations’ or ‘pseudostaminodial scales’ alternating with the true androecial members). Staminodes when present, 1–3, or 2, or 3, or 5; in the same series as the fertile stamens; when present, petaloid, or non-petaloid. Stamens (1–)3–5; reduced in number relative to the adjacent perianth, or isomerous with the perianth; oppositisepalous. Anthers dehiscing via longitudinal slits; introrse; unilocular to bilocular; bisporangiate, or tetrasporangiate. Endothecium developing fibrous thickenings, or not developing fibrous thickenings (very rarely). Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer; of the ‘monocot’ type. Tapetum glandular. Pollen monosiphonous; shed as single grains. Pollen grains aperturate; 6–20 aperturate; foraminate; spinulose; 3-celled.

Gynoecium 2–3 carpelled. The pistil 1 celled. Gynoecium syncarpous; synovarious to eu-syncarpous; superior. Ovary 1 locular; sessile to stipitate. Gynoecium non-stylate, or stylate. Styles 1–3. Stigmas 1–3; dry type; papillate; Group II type. Placentation basal. Ovules in the single cavity 1, or 2–5; ascending, or pendulous (but from a basal funicle, subtribe Achyranthinae, Ptilotus etc.); non-arillate; campylotropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle (rarely), or not contributing to the micropyle. Endothelium not differentiated. Polar nuclei fusing prior to fertilization. Antipodal cells formed; initially 3; proliferating (Pupalia), or not proliferating (usually). Synergids hooked (sometimes with filiform apparatus). Endosperm formation nuclear. Embryogeny solanad, or chenopodiad.

Fruit fleshy, or non-fleshy; not an aggregate; dehiscent, or indehiscent; a capsule, or capsular-indehiscent, or a berry, or a drupe, or a nut (often a utricle or nutlet); without fleshy investment external to the original ovary. Capsules circumscissile (commonly), or splitting irregularly. Seeds non-endospermic (strictly speaking). Perisperm present (abundant, mealy). Seeds with starch. Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous (1/1); curved. The radicle dorsal. Testa smooth (usually shiny).

Physiology, phytochemistry. C3 and C4, or C3-C4 intermediate. C3 physiology recorded directly in Aerva, Achyranthes, Alternanthera, Arthraerua, Celosia, Digera, Pupalia. C4 physiology recorded directly in Achanthochiton, Aerva, Alternanthera, Amaranthus, Brayulinea, Froelichia, Gomphrena, Gossypianthes, Guillemenia, Lithophila, Tidestromia. C3-C4 intermediacy in Alternanthera ficoides and A. tenella. Anatomy C4 type (Acnidia, Achyranthes, Achanthochiton, Aerva, Alternanthera, Amaranthus (see illustration), Brayulinea, Celosia, Froelichia, Gomphrena, Pfaffia, Tidestromia, etc.), or non-C4 type (Achyranthes, Alternanthera, Celosia, Centemopsis, Dasysphaera, Digera, Pupalia, Sericicomopsis etc.). Inulin not found. Cyanogenic, or not cyanogenic. Alkaloids present, or absent. Iridoids not detected. Betalains present (where sought). Saponins/sapogenins present, or absent. Proanthocyanidins absent. Flavonols present, or absent; when present, quercetin. Ellagic acid absent (4 species, 4 genera). Plants often accumulating free oxalates. Sieve-tube plastids P-type; type III (a).

Geography, cytology. Temperate, sub-tropical, and tropical. Widespread. X = 6–13, 17(+).

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae; Caryophyllales. Cronquist’s Subclass Caryophyllidae; Caryophyllales. APG III core angiosperms; core eudicot; Superorder Caryophyllanae. APG IV Order Caryophyllales.

Species 850. Genera 74; Achyranthes, Achyropsis, Acnida, Aerva, Allmania, Alternanthera, Amaranthus, Arthraerua, Blutaparon, Bosea, Brayulinea, Calicorema, Celosia, Centema, Centemopsis, Centrostachys, Chamissoa, Charpentiera, Chionothrix, Cyathula, Dasysphaera, Dasysphaera, Deeringia, Digera, Eriostylos, Froelichia, Gomphrena, Gossypianthus, Guilleminea, Hebanthe, Hemichroa (~ Chenopodiaceae), Henonia, Herbstia, Hermbstaedtia, Indobanalia, Irenella, Iresine, Kyphocarpa, Lagrezia, Leucosphaera, Lithophila, Lopriorea, Marcelliopsis, Mechowia, Nelsia, Neocentema, Nothosaerva, Nototrichium, Nyssanthes, Pandiaka, Pfaffia, Philoxerus, Pleuropetalum, Pleuropterantha, Polyrhabda, Pseudogomphrena, Pseudoplantago, Pseudosericocoma, Psilotrichopsis, Psilotrichum, Ptilotus, Pupalia, Quaternella, Rosifax, Saltia, Sericocoma, Sericocomopsis, Sericorema, Sericostachys, Siamosia, Stilbanthus, Tidestromia, Trichuriella, Volkensinia, Woehleria, Xerosiphon.

Economic uses, etc. A few cultivated ornamentals, e.g. Amaranthus, Gomphrena, Iresine, and some noxious weeds, notably from Amaranthus, Iresine, Acnida.


But propt on beds of amaranth and moly,
How sweet . . . .
To watch the long bright river drawing slowly
His waters from the purple hill -
(Tennyson, ‘Song of the Lotos-eaters’)

Illustrations. • Le Maout and Decaisne: Amaranthus, Gomphrena. • Achyranthes angustifolia: Thonner. • Amaranthus blitum: Eng. Bot. 177, 1867. • Amaranthus polygonoides: R. Wight, Ic. Pl. Indiae Orientalis 2 (1843). • Amaranthus spinosus: R. Wight, Ic. Pl. Indiae Orientalis 2 (1843). • Brandesia villosa: Martius, Nova Gen. et Spec. Pl. Brasiliensium 2 (1826). • Celosia cristata var. coccinea: as C. coccinea, Bot. Reg 1834 (1836). • Deeringia amaranthoides (as D. celosioides): Bot. Mag. 54 (1827). • Froelichia floridana, as Oplotheca: Hook. Ic. Pl. 3 (1840). • Gomphrena desertorum: Martius, Nova Gen. et Spec. Pl. Brasiliensium 2 (1826). • Gomphrena umbellata (as G. pearcei): Hook. Ic. Pl. 11 (1867–71). • Hebanthe spicata: Martius, Nova Gen. et Spec. Pl. Brasiliensium 2 (1826). • Iresine angustifolia, as Rosea elatior: Martius, Nova Gen. et Spec. Pl. Brasiliensium 2 (1826). • Pfaffia glabrata: Martius, Nova Gen. et Spec. Pl. Brasiliensium 2 (1826). • Ptilotus polystachyus: Bot. Reg. 1839, 28. • Ptilotus spathulatus (as Trichinium): Hooker, Fl. Tasmaniae (1860). • Stilbanthus scandens: Hook. Ic. Pl. 13 (1877–79). • Leaf anatomy (Solereder, 1908). • Aerva and Bosea: anomalous stem anatomy (Solereder, 1908).

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: 15th April 2018.’.