The families of flowering plants
~ Formerly Agavaceae, APG Asparagaceae-Nolinoideae.
Habit and leaf form. Generally arborescent (to a few metres tall, with simple or sparingly branched trunks). With terminal aggregations of leaves. Pachycaul. Xerophytic. Leaves alternate (in terminal rosettes); tough and hard or leathery; sessile; sheathing; simple. Lamina entire; linear; parallel-veined.
Leaf anatomy. Stomata with guard-cells rich in oil. The mesophyll containing crystals. The crystals raphides and solitary-prismatic. Foliar vessels present; with scalariform end-walls.
Axial (stem, wood) anatomy. Secondary thickening anomalous. The anomalous secondary thickening from a single cambial ring (cf. Dracaenaceae). The axial xylem without vessels.
Root anatomy. Root xylem with vessels; vessel end-walls simple (?).
Reproductive type, pollination. Unisexual flowers present. Plants dioecious, or polygamodioecious. Floral nectaries present. Nectar secretion from the gynoecium (from septal nectaries).
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in inflorescences; in panicles. Inflorescences panicles, often large and many-flowered, the flowers on articulated pedicels. Flowers regular; 3 merous; cyclic. Perigone tube absent. Hypogynous disk absent.
Perianth of tepals; 6; free; 2 whorled (3+3); isomerous; petaloid (?); similar in the two whorls (?).
Androecium 6. Androecial members free of the perianth; all equal; free of one another; 2 whorled (3+3). Androecium exclusively of fertile stamens. Stamens 6; diplostemonous. Anthers dorsifixed (epipeltate); dehiscing via longitudinal slits. Pollen shed as single grains. Pollen grains aperturate; 1 aperturate; sulcate; 2-celled.
Gynoecium 3 carpelled. Carpels isomerous with the perianth. The pistil 1 celled, or 3 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 1 locular (Dasylirion), or 3 locular. Gynoecium stylate. Styles 1; apical; shorter than the ovary, or about as long as the ovary (relatively short). Placentation when unilocular, basal (Dasylirion); when trilocular, axile (Nolina). Ovules in the single cavity in Dasylirion, 3–6; in Nolina, 2 per locule; anatropous; tenuinucellate. Endosperm formation nuclear.
Fruit non-fleshy (more or less dry, by contrast with Dracaenaceae); indehiscent; capsular-indehiscent, or a samara. Testa without phytomelan; thin.
Seedling. Hypocotyl internode present (short). Seedling collar not conspicuous. Cotyledon hyperphyll compact; non-assimilatory. Coleoptile absent. Seedling cataphylls present. Primary root ephemeral.
Physiology, phytochemistry. Not cyanogenic. Alkaloids absent (?). Saponins/sapogenins present (Nolina). Proanthocyanidins absent. Flavonols present; quercetin. Ellagic acid absent.
Geography, cytology. Holarctic and Neotropical. Warm America.
Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Asparagales. APG 3 core angiosperms; Superorder Lilianae; non-commelinid Monocot; Order Asparagales (as a synonym of Asparagaceae).
Species 45–50. Genera 3–4; Beaucarnea, Nolina, Dasylirion.
General remarks. Differing from Asparagaceae sensu stricto (q.v.) in habit, leaf form and anatomy, stem anatomy, free stamens and non-fleshy fruits.
Illustrations. • Dasylirion quadrangulatum: Bot. Mag. 126 (1900). • Dasylirion, young fruit.
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: 20th July 2017. delta-intkey.com/angio’.