2. Eucnide Zuccarini, Index Seminum (München). 1844: . 1844. name conserved.
Rock or pretty nettle, stingbush [Greek eu-, good or pretty, and knide, nettle, alluding to stinging trichomes and showy flowers] Rock or pretty nettle, stingbush [Greek eu-, good or pretty, and knide, nettle, alluding to stinging trichomes and showy flowers]
Sympetaleia A. Gray
Herbs or subshrubs, annual or perennial; trichomes (1) pointed with surfaces ± smooth, (2) retrorsely barbed along shaft and at apex or only at apex, and (3) stinging. Stems usually erect or spreading, rarely prostrate or pendent on cliffs. Leaves cauline; petiole present; blade ovate, lobed or unlobed, margins crenate or dentate. Inflorescences dichasia and monochasia [solitary flowers]; peduncle inconspicuous [conspicuous]. Pedicels elongating in fruit. Flowers: hypanthium completely adnate to ovary; perianth whorls differentiated; sepals green, distinct, lanceolate, straplike, or narrowly ovate, shorter than petals; petals white, green, or yellow [reddish orange], connate proximally to 1/2+ length, spatulate or ovate, spreading or erect (then corolla essentially tubular) [erect proximally, divaricate distally (corolla salverform)], glabrous except apices sparsely hairy; nectary distal on ovary; stamens 15–150+, exserted or included; filaments monomorphic, filiform, longer or shorter than anthers; anthers without distal connective extension; staminodes absent; pistil 5-carpellate, placentae parietal; stigma lingulate, 5-lobed, papillate. Fruits capsules, dehiscing by apical valves [splitting longitudinally], cup-shaped, straight; sepals persistent. Seeds many, cylindric to ovoid, not dorsiventrally flattened, to 1 mm, not winged. x = 21.
Species 14 (4 in the flora): sw, sc United States, Mexico, Central America (Guatemala).
Eucnide was placed in subfam. Mentzelioideae by I. Urban and E. Gilg (1900), Gilg (1925b), and H. J. Thompson and W. R. Ernst (1967); however, this subfamily is paraphyletic. Eucnide has been placed in molecular phylogenetic studies as sister to the rest of Loasaceae (L. Hufford et al. 2003).
Three sections of Eucnide were recognized by H. J. Thompson and W. R. Ernst (1967). Section Mentzeliopsis H. J. Thompson & W. R. Ernst, consisting only of E. urens, was distinguished on the basis of its floral architecture in which all stamens are shorter than the style and not exserted beyond the corolla. The numerous stamens of E. urens are also tightly positioned around the style. Section Sympetaleia (A. Gray) H. J. Thompson & W. R. Ernst consists of three species that are endemic to the Baja California Peninsula and surrounding islands, except for E. rupestris, which has a distribution that extends into extreme southern California and southwestern Arizona and to Sinaloa and Sonora, Mexico. Species of sect. Sympetaleia have stamens with monothecate, bisporangiate anthers in contrast to other members of the genus, which have more conventional bithecate, tetrasporangiate anthers. All other species of Eucnide were placed in sect. Eucnide by Thompson and Ernst.
Among the North American species of Eucnide, E. urens is the only species found in the Mojave Desert, where it is centered (H. J. Thompson and W. R. Ernst 1967). The other North American species are found in the Chihuahuan and Sonoran deserts and in adjacent areas. All species are found in similar cliff or rocky slope habitats (uncommonly in arroyos and washes). Some species, such as E. bartonioides, have fruit pedicels that are negatively phototropic and elongate extensively, which appear to be adaptations for dispersal on cliffs (Thompson and Ernst).
Most species of Eucnide are self-pollinating (H. J. Thompson and W. R. Ernst 1967), although they generally have some spatial separation between the stigmas and anthers soon after the flowers open that allows for cross-pollination (L. Hufford 1988). Only taxa with the largest flowers, such as E. bartonioides var. bartonioides (possibly pollinated by hawk moths) and E. urens (pollinated by the melittid bee, Hesperaster laticeps), appear to be strictly outcrossing (Thompson and Ernst).
SELECTED REFERENCES Hufford, L. 1987. Inflorescence architecture of Eucnide (Loasaceae). Madroño 34: 18–28. Hufford, L. 1988. Potential roles of scaling and post-anthesis developmental changes in the evolution of floral forms of Eucnide (Loasaceae). Nordic J. Bot. 8: 147–157. Hufford, L. 1988b. Seed coat morphology of Eucnide and other Loasaceae. Syst. Bot. 13: 154–167. Waterfall, U. T. 1959. A revision of Eucnide. Rhodora 61: 231–243.