Malacothrix

Annuals or perennials, 2–70(–200) cm; taprooted (rhizomatous or taproots becoming caudices in M. saxatilis). Stems 1–15 (usually from basal rosettes), usually erect, sometimes ± prostrate, usually branched (scapiform in M. californica), usually glabrous (sometimes piloso-hirsute, stipitate-glandular, or tomentose to arachnose or puberulent, at least proximally or in leaf axils). Leaves usually basal and cauline; sessile; blades mostly oblong or lanceolate to obovate, oblanceolate, or spatulate (often pinnately lobed), ultimate margins entire or ± dentate (faces usually glabrous, sometimes piloso-hirsute or tomentose to arachnose or puberulent). Heads usually in corymbiform to paniculiform arrays (borne singly in M. californica). Peduncles not inflated distally, usually bracteate. Calyculi 0 (outer phyllaries intergrading with inner) or of 3–30+, ± deltate or lanceolate to linear or subulate, subequal to unequal bractlets (in 1–2 series distinct from phyllaries, margins usually hyaline, faces usually glabrous, sometimes arachnose, rarely stipitate-glandular). Involucres usually broadly to narrowly campanulate, sometimes hemispheric, (5–22+ ×) 2–22+ mm diam. Phyllaries either (without calyculi) 25–80+ in 4–6+ series and orbiculate to oblong, lance-oblong, lanceolate, or linear, unequal, or (with calyculi) 12–25+ in 2–3 series and oblong or lanceolate to linear, subequal; margins ± hyaline, 0.05–2.5 mm, apices obtuse to acute or acuminate. Receptacles flat to ± convex, pitted or smooth, sometimes bristly, epaleate. Florets 15–270; corollas yellow or white (sometimes reddish or lavender abaxially; outer ligules exserted 1–15 mm). Cypselae (monomorphic) stramineous to brown or purplish brown, ± prismatic or cylindro-fusiform, not beaked, ribs 15 (often 5 more prominent than others, apices of ribs sometimes projecting and forming coronas subtending pappi), usually glabrous (sometimes minutely hirtellous or muriculate); pappi 0, or (single or double) persistent, whitish, crenate crowns or rings of (1–)8–25+ teeth (mostly 0.05–0.1 mm) plus 0–6, coarse, smooth bristles (setiform scales), all in ± 1 series, subtending (i.e., exterior to) the readily falling, inner (or single and only) pappi of 15–35, basally coherent, white, fine, smooth to barbellulate or (proximally) ± plumose bristles in 1 series (falling all together or in groups). x = 7, 9.

Distribution

w United States, nw Mexico, introduced in South America.

Discussion

Species 20 (18 in the flora).

Selected References

Davis, W. S. 1997. The systematics of annual species of Malacothrix (Asteraceae: Lactuceae) endemic to the California Islands. Madroño 44: 223–244.

Williams, E. W. 1957. The genus Malacothrix (Compositae). Amer. Midl. Naturalist 58: 494–512.

Lower Taxa

Malacothrix californica, Malacothrix clevelandii, Malacothrix coulteri, Malacothrix fendleri, Malacothrix floccifera, Malacothrix foliosa, Malacothrix glabrata, Malacothrix incana, Malacothrix indecora, Malacothrix junakii, Malacothrix phaeocarpa, Malacothrix saxatilis, Malacothrix similis, Malacothrix sonchoides, Malacothrix sonorae, Malacothrix squalida, Malacothrix stebbinsii, Malacothrix torreyi

Key

1	Perennials (sometimes flowering first year)	> 2
1	Annuals	> 3
2	Corollas medium yellow; persistent pappi 0	Malacothrix incana
2	Corollas white (usually each with abaxial purple stripe); persistent pappi of fimbriate crowns or 20–25, blunt teeth (0.01–0.05 mm) plus 0 bristles	Malacothrix saxatilis
3	Involucres hemispheric; phyllaries orbiculate (outer) to oblong or linear, hyaline margins 1–2.5 mm wide	Malacothrix coulteri
3	Involucres usually ± campanulate (to hemispheric in M. sonchoides); bractlets of calyculi and/or phyllaries ovate to lanceolate, linear, or subulate, hyaline margins 0.05–0.3(–1) mm wide	> 4
4	Stems seldom branched (heads usually borne singly on scapiform peduncles); cypsela ribs: 5 more prominent than others	Malacothrix californica
4	Stems branched (heads usually in corymbiform to paniculiform arrays); cypsela ribs ± equal, or 5 more prominent than others	> 5
5	Cauline leaves not or seldom notably reduced distally (Channel Islands, California)	> 6
5	Cauline leaves usually reduced distally (M. clevelandii and M. similis are known from Channel Islands, California)	> 9
6	Persistent pappi usually 0, rarely of 1–2 bristles; pollen 70–100% 3-porate	> 7
6	Persistent pappi of 15–20 teeth (0.01–0.1 mm) plus 1–2 bristles; pollen 70–100% 4-porate	> 8
7	Stems erect or ± prostrate (forming mats); proximal cauline leaves usually fleshy (lobes nearly equal, apices obtuse); San Miguel, Santa Cruz, and Santa Rosa islands	Malacothrix indecora
7	Stems erect (not forming mats); proximal cauline leaves usually not fleshy (lobes usually unequal, apices acute or obtuse); Anacapa, San Clemente, San Nicolas, and Santa Barbara islands	Malacothrix foliosa
8	Calyculi 0; phyllaries 31–49 in 5–6+ series, hyaline margins 0.6–1 mm wide; Anacapa and Santa Cruz islands, California	Malacothrix squalida
8	Calyculi of 7–11 bractlets; phyllaries 9–13 in 2–3 series, hyaline margins 0.1–0.2 mm wide; Anacapa Island, California	Malacothrix junakii
9	Corollas 4–10 mm; outer ligules exserted 1–4 mm	> 10
9	Corollas (7–)10–23+ mm; outer ligules exserted 5–15+ mm	> 14
10	Proximal cauline leaves (pinnately lobed, lobes 3–5 pairs, ± equal, bases white-hairy) ± fleshy; persistent pappi of crenate crowns plus 0 bristles; pollen 70–100% 3-porate.	Malacothrix phaeocarpa
10	Proximal cauline leaves (pinnately lobed or not) not fleshy; persistent pappi of 8–24+ teeth plus 1–2 bristles; pollen 3- or 4-porate	> 11
11	Proximal cauline leaves oblanceolate to lance-linear; corollas pale yellow; cypselae ± cylindro-fusiform or prismatic, 1.2–1.8 mm (ribs extending to apices, 5 more prominent than others); persistent pappi of 14–24+ needlelike teeth plus 1 bristle (mainly California)	> 12
11	Proximal cauline leaves obovate to narrowly oblanceolate; corollas white or pale yellow; cypselae ± cylindro-fusiform, 1.7–2.3 mm (ribs not extending to apices, ± equal); persistent pappi of 8–18 teeth plus 1–2 bristles (Arizona, California, Nevada)	> 13
12	Stems branched mostly distally, glabrous; cauline leaves: margins usually dentate; cypselae (stramineous to brown) 1.2–1.8 mm; pollen 3-porate (mean diam. 25 µm)	Malacothrix clevelandii
12	Stems branched mostly proximally; cauline leaves: margins usually entire; cypselae 1.4–1.7 mm (purplish brown); pollen 4-porate (mean pollen diam. 30 µm)	Malacothrix similis
13	Corollas white or pale yellow; cypselae 1.7–2 mm (bases slightly expanded, distal 0.3 mm smooth); pollen 70–100% 3-porate	Malacothrix sonorae
13	Corollas usually yellow, sometimes white; cypselae 1.7–2.3 mm (bases not expanded, distal 0.1–0.2 mm smooth); pollen 70–100% 4-porate	Malacothrix stebbinsii
14	Proximal cauline leaves pinnately lobed (lobes 2–6+ pairs, filiform or triangular to oblong, subequal to unequal, apices acute), not fleshy, ultimate margins dentate or entire; cypsela ribs ± equal	> 15
14	Proximal cauline leaves pinnately lobed (lobes 3–8 pairs, ± oblong to triangular, ± equal, apices obtuse or acute), ± fleshy, ultimate margins usually dentate; cypsela ribs ± equal or 5 more prominent than others	> 16
15	Proximal cauline leaves usually pinnately lobed (lobes filiform); receptacles bristly; cypselae ± cylindro-fusiform (sometimes weakly 5-angled, ribs extending to apices).	Malacothrix glabrata
15	Proximal cauline leaves sometimes pinnately lobed (lobes relatively broad, triangular to deltate); receptacles not bristly; cypselae ± cylindro-fusiform (ribs not extending to apices, distal 0.3 mm of cypselae smooth)	Malacothrix fendleri
16	Corollas white or yellow (usually with lavender abaxially); cypselae 1.2–2 mm; persistent pappi 0	Malacothrix floccifera
16	Corollas lemon or medium yellow; cypselae 1.8–4 mm; persistent pappi of 12–25+ irregular, blunt teeth plus 0–6 bristles	> 17
17	Distal cauline leaves narrowly triangular to linear (bases usually ± dilated, ± clasping); persistent pappi of crenate crowns or 12–25+ teeth plus 0 bristles.	Malacothrix sonchoides
17	Distal cauline leaves ± elliptic to linear (bases narrowly cuneate); persistent pappi of 12–15 teeth plus 0–6 bristles	Malacothrix torreyi