61. Pennellia Nieuwland, Amer. Midl. Naturalist. 5: 224. 1918.
[For Francis Whittier Pennell, 1886-1952, American botanist]
Sara Fuentes-Soriano, Ihsan A. Al-Shehbaz
Heterothrix (B. L. Robinson) Rydberg, Bull. Torrey Bot. Club 34: 435. 1905, based on Thelypodium Endlicher subgen. Heterothrix B. L. Robinson in A. Gray et al., Syn. Fl. N. Amer. 1(1,1): 178. 1895, not Müller Argoviensis 1860; Lamprophragma O. E. Schulz
Perennials; not scapose; pubescent or glabrous, trichomes simple, with stalked, forked or dendritic ones. Stems erect [ascending], often branched distally. Leaves basal and cauline; petiolate or sessile; basal (withered with age), rosulate, petiolate, blade margins entire, dentate to sinuate, or runcinate; cauline subsessile or sessile [shortly petiolate], blade margins entire [dentate to sinuate]. Racemes (several-flowered, sometimes secund, lax), considerably elongated in fruit. Fruiting pedicels erect, descending, ascending, or divaricate-ascending, slender, (glabrous). Flowers (usually actinomorphic, rarely zygomorphic, cup-shaped); sepals erect, oblong to ovate, lateral pair slightly to strongly saccate basally, (usually pubescent, rarely glabrous); petals white (lavender or purple apically), spatulate to oblanceolate, (± longer than sepals), claw undifferentiated from blade, (apex obtuse); stamens slightly tetradynamous; filaments dilated basally; anthers ovate to oblong, (apex obtuse); nectar glands confluent, subtending bases of stamens. Fruits siliques, sessile or shortly stipitate, linear, not torulose, straight or curved, terete or latiseptate; valves each with prominent or obscure midvein, glabrous or pubescent; replum rounded; septum complete; ovules 40-250 per ovary; style distinct or obsolete; stigma capitate. Seeds uniseriate or biseriate, plump or flattened, winged or not, oblong to ovate; seed coat (reticulate-areolate), mucilaginous or not when wetted; cotyledons accumbent or incumbent. x = 8.
Species 8 (3 in the flora): sw United States, Mexico, Central America, South America.
SELECTED REFERENCES Fuentes-Soriano, S. 2004. A taxonomic revision of Pennellia (Brassicaceae). Harvard Pap. Bot. 8: 173-202. Rollins, R. C. 1980b. The genus Pennellia (Cruciferae) in North America. Contr. Gray Herb. 210: 5-21.
