DRYOPETALON A. Gray, Smithsonian Contrib. Knowl. 5: 11. 1853.

Ihsan A. Al-Shehbaz

Tribe: Thelypodieae Prantl in Engler & Prantl, Nat. Pflanzenfam. III. 2: 155. 1891.

Name derivation: from Greek drys, oak, and petalon, petal, in reference to the superficial resemblance of petal shape to some oak leaves.

Type species: D. runcinatum A. Gray.

Rollinsia Al-Shehbaz, Taxon 31: 422. 1982. Type species: R. paysonii (Rollins) Al-Shehbaz (based on Thelypodium paysonii Rollins).

Herbs, annual or biennial. Trichomes simple or absent. Multicellular glands absent. Stems simple or few-branched. Basal leaves petiolate, rosulate or not, entire or dentate to runcinate or pinnatifid; cauline leaves petiolate or uppermost sometimes subsessile, often not auriculate, entire or dentate to pinnatifid. Racemes many flowered, ebracteate, corymbose, initially congested but later elongated considerably in fruit; rachis straight; fruiting pedicels ascending to divaricate or horizontal, persistent. Sepals oblong to ovate, free, erect to ascending, caducous, equal, base of lateral pair slightly saccate or not; petals white or lavender to purple, erect at base with flaring blade, longer than sepals; blade obovate to spatulate, pinnatifid, deeply 2-lobed, repand, or entire, apex obtuse; claws gradually narrowed from blade to base, shorter than sepals, glabrous or papillate at base, unappendaged, entire; stamens 6, slightly exserted, tetradynamous; filaments wingless, unappendaged, glabrous or papillate at base, free; anthers oblong, not apiculate; lateral nectar glands annular; median glands confluent with laterals; ovules (10–)20–110 per ovary. Fruits dehiscent siliques, linear or rarely linear-oblong, terete or latiseptate, not inflated, unsegmented; valves papery, with a distinct midvein, glabrous, not keeled, torulose or not, wingless, unappendaged; gynophore absent or rarely to 3 mm; replum rounded, visible; septum complete, not veined; style distinct; stigma capitate, entire or rarely slightly 2-lobed. Seeds uniseriate, ovate to oblong, plump, wingless or rarely narrowly winged; seed coat not mucilaginous when wetted; cotyledons accumbent or incumbent. x = 14, 12, 10.

Eight species: NW Mexico, SW United States.

References: Al-Shehbaz (2007f), Rollins (1941d).

                                                Key to the species of Dryopetalon

1. Cauline leaves sessile, auriculate to amplexicaul; fruit 2–3 mm wide; seeds 10–28

     per fruit, winged         ................................................................................................ 8. D. vireckii

1. Cauline leaves petiolate, not auriculate; fruit 0.5–1.5(–2) mm wide; seeds 30–110

     per fruit, wingless.

     2. Plants with flowers.

          3. Petal margin pinnatifid, laciniate, or distinctly dentate.

               4. Bases of petal claws and filaments glabrous; flowers purple or lavender......... 5. D. palmeri

               4. Bases of petal claws and filaments pubescent or distinctly papillate; flowers white.

                   5. Leaves entire or shallowly dentate to crenate; petals 4.5–6 mm.............. 3. D. crenatum

                   5. Leaves pinnatifid to runcinate; petals 6–12 mm.................................. 7. D. runcinatum

          3. Petal margin entire or repand, rarely with a few obscure teeth.

               6a. Bases of petal claws and filaments pubescent............................................. 6. D. paysonii

               6b. Bases of petal claws and filaments glabrous.

                   7. Petal apex deeply emarginate; cauline leaves entire or dentate..... 4. D. membranifolium

                   7. Petals apex obtuse; at least some cauline leaves pinnately lobed.

                        8. Petals 5–6.5 ´ 2–2.5 mm, white; ovary or young fruit stipitate......... 1. D. breedlovei

                        8. Petals 7–10 ´ 4–5.5 mm, lavender; ovary or young fruit sessile................. 2. D. byei

     2. Plants with mature fruits.

          9. Cauline leaves entire, rarely shallowly dentate or crenate.

               10. Fruits 1.1–1.5 mm wide; fruiting pedicels 5–11(–13) mm; style 1.5–2.5 mm;

                   petals dentate, obtuse at apex................................................................... 3. D. crenatum

               10. Fruits 0.7–0.9 mm wide; fruiting pedicels 14–20 mm; style 0.5–0.9 mm; petals

                   entire, emarginate at apex.............................................................. 4. D. membranifolium

          9. At least some cauline leaves pinnately lobed.

               11. Fruits sessile or rarely subsessile and with a gynophore 0.1–0.4 mm.

                   12. Style 1.5–2.5 mm; cotyledons incumbent; petals entire................................. 2. D. byei

                   12. Style 0.1–0.7(–1) mm; cotyledons accumbent; petals pinnatifid........ 7. D. runcinatum

               11. Fruits on a distinct gynophore 1–3 mm, if shorter then petals purple.

                   13. Fruits 0.5–0.8 mm wide; seeds 0.6–0.9 ´ 0.5–0.6 mm; stigma slightly 2-lobed

                                       ........................................................................................... 1. D. breedlovei

                   13. Fruits 1.3–2 mm wide; seeds 1–1.7 ´ ca. 1 mm; stigma entire.

                        14. Style cylindrical; gynophore 0.6–1 mm; uppermost leaves coarsely dentate;

                             petals purple or lavender, dentate to laciniate...................................... 5. D. palmeri

                        14. Style often conical; gynophore 1–3 mm; all leaves pinnatifid; petals

                             white, entire...................................................................................... 6. D. paysonii