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Revision of Spathacanthus Generic Description & Key to Species Thomas F. Daniel Department of Botany California Academy of Sciences Golden Gate Park San Francisco, CA 94118

Main Characteristics Phylogenetic Analysis Generic Description & Key to Species S. hahnianus Additional Specimens Examined S. hoffmannii Additional Specimens Examined S. parviflorus Additional Specimens Examined Acknowledgments & Literature Cited Figure Legend: Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Spathacanthus Baill. Hist. Pl. 10: 444. 1891.--TYPE: S. hahnianus Baill. Shrubs or small trees with cystoliths, stems sometimes with conspicuous protruding or blisterlike lenticels. Leaves opposite, subsessile to petiolate, entire. Inflorescence of terminal dichasiate racemes (or thyrses); dichasia opposite, mostly 1-flowered, sessile (to pedunculate), subtended by a bract. Bracts opposite, green, ± inconspicuous, entire. Flowers subtended by 2 homomorphic bracteoles, pedicellate, pedicels usually enlarged in fruit. Calyx green or yellowish, spathaceous, beaked in bud, equally or unequally divided into 2 segments, 1 segment comprising 2 fused lobes, apically entire to 2-lobed, the other segment comprising 3 fused lobes, apically entire to 3-lobed. Corolla white or yellow, externally glabrous (although margins of lobes sometimes ciliolate), tube expanded distally into a ± distinct throat, limb bilabiate (or appearing ± regular), upper lip deeply 2-lobed, lower lip deeply 3-lobed, corolla lobes imbricate (ascending cochlear) in bud. Stamens 4, didynamous, inserted at base of corolla throat, included in corolla tube, anthers 2-thecous, thecae equal in size, parallel, equally inserted, lacking basal appendages, direction of dehiscence (as observed in 2 specimens): anterior pair dehiscing toward upper lip and posterior pair dehiscing toward lower lip; pollen prolate spheroidal to euprolate, 3 (--4)-colporate, 6 (--8)-pseudocolpate, pairs of pseudocolpi sometimes fused near 1 or both poles thereby forming pseudocolpal arcs or ellipses in mesocolpia, exine foveolate to fossulate to verrucate to rugulate; staminodes 0. Style included in corolla tube, glabrous, stigma 2-lobed, lobes equal. Capsule stipitate, very large, glabrous. Seeds 4, homomorphic, borne on retinacula, flattened, lacking trichomes. A genus of three species occurring in southern Mexico and Central America. Plants occur in moist to wet forests. Key to the Species of Spathacanthus 1. Calyx at anthesis equally or subequally divided into 2 prominent segments; corolla 73--97 mm long; capsule 50--89 mm long; Costa Rica S. hoffmannii. 1. Calyx at anthesis unequally divided into 2 (rarely more) prominent segments; corolla 23--70 mm long; capsule 40--62 mm long.         2. Corolla white, 23--29 mm long, throat 5--7.5 mm in diameter, limb 5--8 mm in diameter with lobes 1--3 mm long; calyx yellow prior to fruiting; Mexico and Guatemala on the Pacific slope S. parviflorus.         2. Corolla yellow, 46--70 mm long, throat 9.5--16 mm in diameter, limb 22--45 mm in diameter with lobes (5--) 8--15 mm long; calyx green prior to fruiting; Mexico, Guatemala, and Honduras on the Caribbean slope S. hahnianus.