Lasthenia sect. Ornduffia

Annuals. Leaves usually pinnatifid, sometimes entire. Involucres hemispheric or obconic. Phyllaries persistent, usually distinct (connate 1/4–1/2 their lengths in L. conjugens). Receptacles conic or dome-shaped, glabrous or hairy. Ray corollas yellow, laminae 5–10 mm, floral pigments remaining yellow in dilute aqueous alkali. Disc corolla lobes 5; anther appendices linear, obovate, or ovate (style apices deltate with apical tufts of hairs and subapical fringes of shorter hairs). Cypselae to 1.5 mm; epappose or pappose. 2n = 12.

Distribution

Calif.

Discussion

Species 3 (3 in the flora).

Members of sect. Ornduffia are morphologically similar; they can be distinguished by pappus and phyllary differences. They are typically found in vernal pools; the plants may start growing as submerged aquatics and flower as succulent xerophytes. Leaves of this section are usually pinnatifid; undivided leaves are sometimes produced in crowded conditions with poor light.

R. Ornduff (1966b) originally included the three members of Lasthenia sect. Ornduffia in sect. Ptilomeris. Molecular studies (R. Chan 2000) showed that the three species form a distinct, monophyletic group.

Selected References

Crawford, D. J. and R. Ornduff. 1989. Enzyme electrophoresis and evolutionary relationships among three species of Lasthenia (Asteraceae: Heliantheae). Amer. J. Bot. 76: 289–296.

Lower Taxa

Lasthenia burkei, Lasthenia conjugens, Lasthenia fremontii

Key

1	Phyllaries 12–18 (connate 1/4–1/2 their lengths)	Lasthenia conjugens
1	Phyllaries 7–16 (distinct)	> 2
2	Pappi usually of 1(–2) aristate scales plus 3–6+ shorter, ± subulate scales	Lasthenia burke
2	Pappi usually of (3–)4(–5) subulate, aristate scales plus 3–5+ shorter, ± subulate scalesor teeth, rarely of aristate scales only or 0	Lasthenia fremontii