| | The Families of Angiosperms |
~ Asparagaceae-Agavoideae p.p., former Liliaceae
Including Yuccaceae J.G. Agardh; excluding Doryanthaceae, Dracaenaceae, Phormiaceae.
Habit and leaf form. Herbs, or shrubs, or ‘arborescent’ (often ‘rosette trees’). Plants succulent, or non-succulent; green and photosynthesizing. Perennial; with a basal aggregation of leaves, or with terminal aggregations of leaves (when shrubby or arborescent); rhizomatous. Self supporting, or epiphytic. Often pachycaul. Xerophytic. Leaves persistent; small to very large; alternate; spiral; flat, or terete; leathery, or fleshy, or leathery and fleshy; sessile; sheathing; with blades borne edgewise to the stem, or with blades ‘normally orientated’; simple; epulvinate. Lamina entire; linear, or lanceolate, or subulate; parallel-veined; without cross-venules. Lamina margins entire, or serrate (often sharp pointed and with lateral spines). Leaf development ‘graminaceous’.
General anatomy. Plants without silica bodies.
Leaf anatomy. Stomata present; anomocytic. The mesophyll not containing mucilage cells; containing crystals. The crystals raphides and solitary-prismatic. Foliar vessels absent.
Axial (stem, wood) anatomy. Nodes multilacunar. Primary vascular tissues consisting of scattered bundles. Secondary thickening absent, or anomalous (e.g. Agave, Furcraea, Yucca). The anomalous secondary thickening when present, from a single cambial ring. The axial xylem without vessels.
Root anatomy. Root xylem with vessels; vessel end-walls scalariform, or simple.
Reproductive type, pollination. Unisexual flowers present, or absent. Plants hermaphrodite (usually), or andromonoecious, or gynomonoecious, or dioecious. Floral nectaries present. Nectar secretion from the gynoecium (from septal nectaries).
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. The ultimate inflorescence units cymose (but often condensed). Inflorescences scapiflorous, or not scapiflorous; terminal; usually large, much-branched panicles. Flowers bracteate; regular to somewhat irregular; when irregular, somewhat zygomorphic; 3 merous; cyclic; pentacyclic. Perigone tube present, or absent.
Perianth of ‘tepals’; 6; free, or joined (below); 2 whorled; isomerous; petaloid; similar in the two whorls. Tepal apex trichomes (TAT) present (Agave, Furcraea, Yucca).
Androecium 6. Androecial members adnate (to the perianth tube), or free of the perianth; all equal; free of one another; 2 whorled. Androecium exclusively of fertile stamens, or including staminodes. Staminodes when present, 3. Stamens 3, or 6; isomerous with the perianth, or diplostemonous. Anthers dorsifixed; dehiscing via longitudinal slits; usually introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Microsporogenesis successive. The initial microspore tetrads tetrahedral, or isobilateral, or linear. Anther wall of the ‘monocot’ type. Tapetum glandular. Pollen shed in aggregates (rarely), or shed as single grains; in Agave, occasionally in tetrads. Pollen grains aperturate; 1 aperturate, or 2 aperturate; sulcate, or sulculate; 2-celled.
Gynoecium 3 carpelled. The pistil 3 celled. Gynoecium syncarpous; eu-syncarpous; superior to inferior. Ovary 3 locular. Gynoecium stylate. Styles 1; apical. Stigmas wet type, or dry type; papillate; Group II type, or Group III type, or Group IV type. Placentation axile. Ovules 6–50 per locule (i.e. ‘several to many’); anatropous; crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating. Synergids pear-shaped (sometimes with filiform apparatus). Endosperm formation helobial, or nuclear (rarely).
Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule, or a berry. Capsules loculicidal. Seeds endospermic. Endosperm oily. Seeds without starch. Cotyledons 1. Embryo achlorophyllous (2/2 — Agave, Yucca); straight. Testa encrusted with phytomelan; black (where recorded).
Seedling. Hypocotyl internode present (short). Seedling collar not conspicuous. Cotyledon hyperphyll somewhat to much elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling cataphylls absent. First leaf dorsiventral. Primary root persistent.
Physiology, phytochemistry. CAM. CAM recorded directly in Agave, Hesperaloë, Polianthes, Yucca (non-succulent). Accumulated starch other than exclusively ‘pteridophyte type’. Not cyanogenic. Alkaloids absent (?). Saponins/sapogenins present (richly, steroidal, including those of Agave and Yucca which constitute active principles of contraceptive pills). Proanthocyanidins absent. Flavonols present (Agave), or absent; in Agave, kaempferol. Ellagic acid absent.
Geography, cytology. Holarctic and Neotropical. Madrean. Sub-tropical to tropical. Widespread. X = 30 (consistently).
Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Asparagales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Asparagales (as a synonym of Asparagaceae).
Species about 400. Genera 9; Agave, Beschorneria, Diuranthera (?), Furcraea, Hesperaloë, Littaea, Manfreda, Polianthes, Prochnyanthes, Sansevieria, Yucca.
General remarks. Conspicuously differing from Asparagaceae sensu stricto (q.v.) in habit and associated characters; also in assorted ‘esoteric characters’ which, in view of limited sampling, are of questionable taxonomic worth (e.g., xylem without vessels, the CAM physiology, seedlings without cataphylls.).
Economic uses, etc. Pulque and mescal derive from fermentation/distillation of Agave sap; and many Agave and Yucca species yield useful fibres (sisal hemp, henequen, pita, istle, ixtle, lechuguilla, keratto, etc.).
Illustrations. • Le Maout and Decaisne: Agave. • Agave americana, Littaea geminiflora and Yucca aloifolia - habit: Lindley. • Agave coetocapnia (as Bravoa geminiflora): Bot. Mag. 79 (1853). • Agave decipiens (as A. laxifolia): Bot. Mag. 122 (1896). • Agave elemeetiana: Bot. Mag. 114 (1888). • Agave horrida: Bot. Mag. 106 (1880). • Agave mitis (as A. haseloffii): Bot. Mag. 123 (1896). • Agave pendula (as A. sartorii): Bot. Mag. 103 (1877). • Agave potatorum (as A. saundersii): Bot. Mag. 91 (1865). • Agave scabra: Bot. Reg. 1839, 55. • Agave schidigera: Bot. Mag. 93(1867). • Agave schottii: Bot. Mag. 123 (1897). • Agave watsonii: Bot. Mag. 134 (1908). • Beschorneria tubiflora (as B. tonelii): Bot. Mag. 100 (1874). • Beschorneria wrightii: Bot. Mag. 127 (1901). • Beschorneria yuccoides: Bot. Mag. 86 (1860). • Beschorneria yuccioides subsp. dekosteriana: Bot. Mag. 110 (1884). • Chlorophytum longifolium (as Dasystachys drimiopsis): Bot. Mag. 124 (1898). • Diuranthera major: Hook. Ic. Pl. 28 (1902). • Furcraea hexapetala, as F. macrophylla: Hook. Ic. Pl. 26 (1897). • Furcraea longaeva (as Fourcroya): Bot. Mag. 91 (1865). • Furcraea selloa, as F. flavo-viridis: Bot. Mag. 86 (1860). • Furcraea selloa (as Fourcroya): Bot. Mag. 101 (1875). • Furcraea undulata: Bot. Mag. 101 (1875). • Furcraea undulata (as F. pubescens): Bot. Mag. 118 (1892). • Hesperaloe parviflora (as H. yuccaefolia): Bot. Mag. 126 (1900). • Sansevieria kirkii: Bot. Mag. 120 (1894). • Yucca aloifolia: as Y. draconis, Bot. Reg. 1894 (1836). • Yucca elata: Bot. Mag. 125 (1899). • Yucca cf. flaccida, filamentosa: as Y. flaccida, Bot. Reg. 1895 (1836). • Yucca filifera: Bot. Mag.117 (1891). • cf. Yucca gloriosa: as Yucca superba, Bot. Reg. 1690, 1835. • Yucca filamentosa and whipplei (Chittenden). • Yucca rupicola: Bot. Mag. 117 (1891).
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: 4th May 2024. delta-intkey.com’.
