Washingtonia
Bot. Zeitung (Berlin) 37: 68, 148. 1879.
Plants tree palms. Stems solitary, erect, tall, massive in one species (more than 10020 cm diam.)(100–150 cm diam.), partly or completely covered with old leaf bases and marcescent dry leaves forming conspicuous skirt around trunk. Leaves: sheath fibers soft; petiole split at base, conspicuously armed with teeth along margins, sometimes unarmed in tall plants; abaxial hastula absent; adaxial hastula irregularly shaped, margin becoming tattered, fibrous; costa prominent; blade costapalmate; plication induplicate; segments lanceolate, basally connate, bearing fibers between segments; apices 2-cleft or irregularly tattered into fibers. Inflorescences axillary within crown of leaves, paniculate, arching well beyond leaves, with 2 orders of branching; prophyll leathery; rachis bracts very conspicuous, tubular at base, distally flattened and leathery, long; rachillae glabrous. Flowers bisexual, borne singly along rachillae, short- pedicellate; perianth 2-seriate; calyx cupulate, 3-lobed, apices and margins irregular; petals 3, long, chaffy, basally connate into tube; stamens 6, adnate briefly to petals; pistils 3, distinct basally, glabrous; styles connate, slender, long; stigma inconspicuous. Fruits drupes, blackish, ellipsoid; exocarp smooth; mesocarp thin, fleshy; endocarp thin. Seeds ellipsoid; endosperm homogeneous; embryo basal; eophyll undivided, lanceolate. n = 18.
Distribution
w North America, nw Mexico.
Discussion
The two species are easy to distinguish when cultivated side by side, but they are sometimes difficult to identify from herbarium specimens. Analysis of flavonoids (S. Zona and R. Scogin 1988) can reliably distinguish the two species.
Species 2 (2 in the flora).
Selected References
Lower Taxa
Key
| 1 | Trunk greater than 100 cm diam. | Washingtonia filifera |
| 1 | Trunk less than 80 cm diam. | Washingtonia robusta |