[Greek chylos, juice or succulence, and -isma, condition, alluding to fleshy leaves of C. scapoidea, the type species]

Warren L. Wagner

Oenothera Linnaeus [unranked] Chylismia Torrey & A. Gray, Fl. N. Amer. 1: 506. 1840; Camissonia Link sect. Chylismia (Torrey & A. Gray) P. H. Raven; Oenothera sect. Chylismia (Torrey & A. Gray) P. H. Raven; Oenothera subg. Chylismia (Torrey & A. Gray) Jepson

Herbs, usually annual, sometimes perennial, rarely biennial, usually caulescent. Stems ascend­ing to erect, usually branched. Leaves basal and cauline, cauline often reduced, basal often forming well-developed rosette, alternate; stipules absent; long-petiolate; blade often pin­nately (rarely bipinnately) lobed, sometimes unlobed, or lateral lobes greatly reduced or absent, ter­minal lobe usually large, margins usually regularly or irregularly dentate to serrate, sometimes denticu­late, serrulate, or entire, abaxial surface or margin with ± conspicuous, usually brown, oil cells. Inflorescences racemes, erect or nodding. Flowers bisexual, actinomorphic, buds usually erect, sometimes reflexed; floral tube deciduous (with sepals, petals, and stamens after anthesis), with basal nectary; sepals 4, reflexed singly; petals 4, usually yellow or white, often fading orange-red, sometimes lavender or purple, rarely cream, often with 1+ red dots near base; stamens usually 8, in 2 subequal series, rarely 4 in 1 series (usually in C. exilis), anthers versatile, pollen shed singly or in tetrads; ovary 4-locular, stigma usually entire and capitate, rarely conical-peltate and ± 4-lobed, surface unknown, probably wet and non-papillate. Fruit a capsule, straight or slightly curved, subterete and clavate or oblong-cylindrical, regularly loculicidal; pedicellate. Seeds numerous, in 2 rows per locule, lenticular to narrowly ovoid to narrowly obovoid, finely pitted, with ± pronounced membranous margin when immature. x = 7.

Species 16 (16 in the flora): w United States, nw Mexico.

Chylismia is distinguished from other genera formerly included in Camissonia by straight to arcuate (never twisted or curled) capsules on distinct pedicels and seeds in 2 rows per locule. R. A. Levin et al. (2004) included only one species each from Camissonia sects. Chylismia and Lignothera; the two formed a moderately supported branch, which led W. L. Wagner et al. (2007) to recognize Chylismia as a distinct genus. Chylismia is strongly supported in a sister relationship to the realigned Oenothera. This clade is in turn sister to Eulobus. Reproductive features include: self-incompatible (C. brevipes, C. claviformis, C. multijuga, C. munzii, and probably C. confertiflora, C. eastwoodiae, and C. parryi; P. H. Raven 1962, 1969) or self-compatible; flowers diurnal, outcrossing and pollinated by mostly oligolectic bees or autogamous, or opening one to two hours before sunset (in one subspecies of C. claviformis and the two species of sect. Lignothera); the evening-opening subspecies of C. claviformis pol­linated mostly by oligolectic bees and moths, C. cardiophylla mainly by small moths, and C. arenaria, with its long floral tubes, by hawkmoths (E. G. Linsley et al. 1963, 1963b, 1964). Most species are diploid (2n = 14) but there are occasional tetraploids (2n = 28); floating translocations are relatively common (Raven 1962, 1969).

SELECTED REFERENCE Raven, P. H. 1962. The systematics of Oenothera subgenus Chylismia. Univ. Calif. Publ. Bot. 34: 1–122.