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The families of flowering plants

L. Watson and M.J. Dallwitz

Iridaceae Juss.

Including Gladiolaceae Rafin., Hewardiaceae Nak., Isophysidaceae Takhtajan, Spathaceae Dulac; excluding Geosiridaceae.

Habit and leaf form. Herbs, or shrubs (rarely). ‘Normal’ plants. Plants green and photosynthesizing. Perennial; with a basal aggregation of leaves, or without conspicuous aggregations of leaves; rhizomatous, or cormous, or bulbaceous (a few). Helophytic to xerophytic. Leaves persistent, or deciduous; alternate; usually distichous; flat, or terete; ‘herbaceous’, or leathery; sessile, or petiolate; sheathing. Leaf sheaths with free margins, or with joined margins (exemplified in Sisyrinchium). Leaves foetid (sometimes), or without marked odour; borne edgewise to the stem (commonly), or ‘normally orientated’ (with Iris exhibiting both conditions); simple; epulvinate. Lamina entire; linear, or lanceolate; parallel-veined; without cross-venules. Leaves eligulate. Lamina margins entire. Leaf development ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral, or bifacial, or centric. Stomata present; anomocytic. Lamina with secretory cavities. Secretory cavities containing mucilage. The mesophyll not containing mucilage cells; containing crystals. The crystals solitary-prismatic. Foliar vessels mostly absent. Minor leaf veins without phloem transfer cells (Iris).

Axial (stem, wood) anatomy. Secretory cavities present; with mucilage. Secondary thickening absent, or anomalous (in Aristea, Klattia, Nivenia, Witsenia). The anomalous secondary thickening when present, from a single cambial ring. The axial xylem without vessels (usually), or with vessels (Sisyrinchium).

The vessel end-walls in Sisyrinchium, scalariform and simple (mostly simple).

Root anatomy. Root xylem with vessels; vessel end-walls scalariform (mostly), or scalariform and simple, or simple (Sisyrinchium).

Reproductive type, pollination. Plants hermaphrodite. Floral nectaries present (mostly), or absent. Nectar secretion from the perianth (mostly, from nectaries at the tepal bases), or from the gynoecium (septal nectaries in Ixioideae). Pollination entomophilous, or ornithophilous, or anemophilous (rarely).

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in panicles, or in cymes, or in spikes, or in umbels, or in corymbs. The ultimate inflorescence units when more than one-flowered, cymose, or racemose. Inflorescences nearly always scapiflorous (but some with the inflorescence reduced to a single, almost sessile flower); terminal; panicles, thyrses, cymes, spikes — often hard to interpret; spatheate (via one or two expanded, bladeless sheaths). Flowers bracteate; small to large; regular to very irregular; when irregular, zygomorphic; 3 merous; cyclic; tetracyclic (usually). Perigone tube present (long or short).

Perianth of ‘tepals’; 6; joined; 2 whorled; isomerous; petaloid; without spots, or spotted (commonly); similar in the two whorls, or different in the two whorls (the inner sometimes much smaller); white, or yellow, or red, or purple, or violet, or blue (or blue-green). Tepal apex trichomes (TAT) absent (17 genera).

Androecium (2–)3. Androecial members free of the perianth, or adnate (to the perianth tube); free of one another, or coherent (the filaments often united into a basal tube); when united, 1 adelphous; 1 whorled (representing the outer whorl). Androecium exclusively of fertile stamens. Stamens (2–)3; reduced in number relative to the adjacent perianth to isomerous with the perianth; alterniperianthial (opposite the outer perianth lobes). Anthers separate from one another (usually), or cohering (sometimes, e.g. Homeria spp); basifixed; dehiscing via longitudinal slits; extrorse. The endothecial thickenings spiral. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Pollen grains aperturate (usually), or nonaperturate; 1 aperturate (usually), or 2 aperturate; sulcate (usually), or spiraperturate, or sulculate (Tia); 2-celled (in 9 genera).

Gynoecium 3 carpelled; partly petaloid (commonly), or non-petaloid. The pistil 3 celled (nearly always), or 1 celled (Isophysis). Gynoecium syncarpous; synstylovarious; inferior (nearly always), or superior (very rarely —Isophysis). Ovary 3 locular, or 1 locular (Isophysis). The ‘odd’ carpel anterior. Gynoecium stylate. Styles 1, or 3, or 6 (depending on interpretation, being 3-lobed with the lobes sometimes very deeply subdivided and slender (see Nemastylis), or these expanded and petaloid); apical. Stylar canal present. Stigmas dry type; papillate; Group II type. Placentation when unilocular (i.e. very rarely), parietal; nearly always axile. Ovules (1–)2–50 per locule (i.e. to ‘many’); arillate, or non-arillate; anatropous; bitegmic; crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; persistent. Synergids pear-shaped, or hooked (sometimes with filiform apparatus). Endosperm formation nuclear.

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Seeds endospermic. Endosperm oily. Seeds usually without starch. Cotyledons 1 (coleoptile-like). Embryo achlorophyllous (3/5), or chlorophyllous (Tritonia crocosmifolia); straight (small). Testa without phytomelan; membranous or thick.

Seedling. Hypocotyl internode present (usually short), or absent. Mesocotyl absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated, or compact; assimilatory (sometimes when elongated), or non-assimilatory; when elongated, more or less circular in t.s. Coleoptile present (e.g. Aristea), or absent. Seedling cataphylls present (e.g. Neomarica), or absent. First leaf ensiform. Primary root ephemeral.

Physiology, phytochemistry. C3. C3 physiology recorded directly in Iris, Sisyrinchium. Anatomy non-C4 type (Sisyrinchium). Accumulated starch other than exclusively ‘pteridophyte type’. Cyanogenic, or not cyanogenic (usually). Alkaloids present (commonly), or absent. Anthraquinones detected (Gladiolus, Libertia); polyacetate derived. Arbutin absent. Saponins/sapogenins present, or absent. Proanthocyanidins present (in 3 genera), or absent (more often); when present, cyanidin and delphinidin. Flavonols present (e.g. Gladiolus), or absent (mostly); when present, kaempferol and quercetin. Ellagic acid absent. Sieve-tube plastids P-type; type II.

Geography, cytology. Holarctic, Paleotropical, Neotropical, Cape, and Australian. Temperate to tropical. Almost cosmopolitan, but lacking from frigid zones and northern Eurasia. X = 3–19 (or more).

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Liliales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Asparagales.

Species 1800. Genera 92; Ainea, Alophia, Anomatheca, Aristea, Babiana, Barnardiella, Belamcanda, Bobartia, Calydorea, Cardenanthus, Chasmanthe, Cipura, Cobana, Crocosmia, Crocus, Cypella, Devia, Dierama, Dietes, Diplarrhena, Duthiastrum, Eleutherine, Ennealophus, Ferraria, Fosteria, Freesia, Galaxia, Geissorhiza, Gelasine, Geosiris, Gladiolus, Gynandriris, Herbertia, Hermodactylus, Hesperantha, Hesperoxiphion, Hexaglottis, Homeria, Homoglossum, Iris, Isophysis, Ixia, Kelissa, Klattia, Lapeirousia, Lethia, Libertia, Mastigostyla, Melasphaerula, Micranthus, Moraea, Nemastylis, Neomarica, Nivenia, Olsynium, Onira, Orthrosanthus, Pardanthopsis, Patersonia, Pillansia, Pseudotrimezia, Radinosiphon, Rheome, Roggeveldia, Romulea, Savannosiphon, Schizostylis, Sessilanthera, Sisyrinchium, Solenomelus, Sparaxis, Sympa, Syringodea, Tapeina, Thereianthus, Tigridia, Trimezia, Tritonia, Tritoniopsis, Tucma, Watsonia, Wisenia, Zygotritonia.

Economic uses, etc. Numerous ornamentals, plus orris root (from Iris rhizomes) and saffron dye (from Crocus stigmas).


And with its reeds the wandering stream
Reflects the flag-flower’s golden beam
(Charlotte Smith, quoted by Ann Pratt, ‘Wild Flowers’ (1857) - Iris pseud-acorus)

Say, what impels, amidst surrounding snow
Congeal’d, the crocus, flamy bud to glow?
Say, what retards, amidst the summer’s blaze,
Th’ autumnal bulb, till pale, declining days
(Gilbert White, ‘Natural History of Selbourne’, 1788 - on spring versus autumn flowering, in closely related species of Crocus)

Illustrations. • Le Maout and Decaisne: Iris, Pardanthus (= Belamcanda). • Le Maout and Decaisne: Crocus vernus, Hydrotaenia (= Tigridia). • Lapeyrousia fabricii: Thonner. • Babiana ringens: Bot. Mag. 109 (1883). • Babiana spathacea: Hook. Ic. Pl. 28 (1901). • Crocosima fucata: as Tritonia, Bot. Reg. XXIV, 35 (1838). • Crocus biflorus var. pusillus(?): as C. pusillus, Bot. Reg. 1987, 1837. • Crocus imperati: Bot. Reg. 1993, 1837. • Crocus nudiflorus: Eng. Bot. 1500 (1869). • Crocus speciosus: Bot. Reg. 1839, 040. • Crocus vernus: Bot. Mag. 2 (1788). • 'Croci autumnales' (see Notes): 5 species, Bot. Reg. 1844, 3. • Dierama pendulum: as Sparaxis pendula, Bot. Reg. 360, 1830. • Hydrotaenia meleagris: Bot. Reg. 39, 1842. • Iris alata: Bot. Reg 1876 (1836). • Iris foetidissima (B. Ent.). • Iris kolpakowskianum, as Xiphion: Bot. Mag. 106 (1880). • Iris pseudacorus (B. Ent.). • Iris sibirica: Bot. Mag. 2 (1788). • Iris spuria: Bot. Mag. 2 (1788). • Iris orientalis, as I. ochroleuca: Bot. Mag. 2 (1788). • Lapeyrousia anceps: Bot. Reg. 1903 (1836). • Libertia pulchella (as lawrencei): Hooker, Fl. Tasmaniae (1860). • Nemastylis geminiflora, as N. acuta: Bot. Mag. 109 (1883). • Patersonia occidentalis: flower (photo). • Patersonia occidentalis: habit (photo). • Patersonia occidentalis var. occidentalis: Bot. Reg. 1839, 60. • Rigidella flammea: Bot. Reg. xxvi, 16 (1840). • Rigidella immaculataa: Bot. Reg. 68, 1841. • Sisyrinchium graminifolium: Bot. Reg. 1915 (1836).

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.’.