Excluding Doryanthaceae, Dracaenaceae, Phormiaceae
Habit and leaf form. Herbs, or shrubs, or `arborescent' (often `rosette trees'). Leaves well developed. Plants succulent, or non-succulent. 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 evergreen; small to very large; alternate; spiral; flat, or terete; leathery, or fleshy, or leathery and fleshy; sessile; sheathing; edgewise to the stem, or with `normal' orientation; 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). Leaves with a persistent basal meristem, and basipetal development.
General anatomy. Plants without silica bodies. Accumulated starch other than exclusively `pteridophyte type'.
Leaf anatomy. Stomata present; anomocytic.
The mesophyll not containing mucilage cells; containing calcium oxalate crystals. The mesophyll crystals solitary-prismatic (no raphides). Vessels absent.
Stem anatomy. Nodes multilacunar. Primary vascular tissue in scattered bundles. Secondary thickening absent, or anomalous; when present, from a single cambial ring. Xylem without vessels.
Root anatomy. Root xylem with vessels. Vessel end-walls scalariform, or simple.
Reproductive type, pollination. Hermaphrodite (usually), or andromonoecious, or gynomonoecious, or dioecious.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in `inflorescences'; in panicles. The terminal inflorescence unit 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.
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 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; syncarpous; eu-syncarpous; superior to inferior. Ovary 3 locular. 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.
Physiology, biochemistry. Not cyanogenic. Alkaloids absent (?). Proanthocyanidins absent. Flavonols present (Agave), or absent; in Agave, kaempferol. Ellagic acid absent. Saponins/sapogenins present (richly, steroidal, including those of Agave and Yucca which constitute active principles of contraceptive pills). CAM. CAM recorded in Agave, Polianthes, Yucca (non-succulent).
Geography, cytology. Holarctic and Neotropical. Sub-tropical to tropical. Widespread. X = 30 (consistently).
Taxonomy. Subclass Monocotyledonae. Superorder Liliiflorae; Asparagales. Species about 400. Genera 9; Agave, Beschorneria, Furcraea, Hesperaloë, Littaea, Manfreda, Polianthes, Prochnyanthes, Yucca.
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. agava156.gif agava787.gif
