~ Agavaceae
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.
Vessels present; end-walls scalariform.
Stem anatomy. Secondary thickening anomalous; from a single cambial ring (cf. Dracaenaceae). Xylem without vessels.
Root anatomy. Root xylem with vessels. Vessel end-walls simple (?).
Reproductive type, pollination. 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.
Gynoecium 3. Carpels isomerous with the perianth. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 1 locular (Dasylirion), or 3 locular. Gynoecium stylate. Styles 1; apical; shorter than the mature ovary, or about as long as the mature 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. Testa without phytomelan.
Physiology, biochemistry. Not cyanogenic. Alkaloids absent (?). Proanthocyanidins absent. Flavonols present; quercetin. Ellagic acid absent. Saponins/sapogenins present (Nolina).
Geography, cytology. Holarctic and Neotropical. Warm America.
Taxonomy. Subclass Monocotyledonae. Superorder Liliiflorae; Asparagales. Species 45-50. Genera 3-4; Nolina, Dasylirion.
Illustrations. nolin863.gif
