Zigadenus

Herbs, perennial, subscapose, bulbous or rhizomatous, all parts containing toxic alkaloids; roots contractile. Leaves usually fewer than 10, mostly basal, alternate, simple, distal ones reduced and grading into floral bracts, sometimes completely sheathing at the base; blade with venation parallel, linear, glabrous, margins entire. Inflorescences terminal, racemose, corymbose, or paniculate, 5–125-flowered, glabrous. Flowers usually bisexual, but often staminate on branches in panicles, protandrous, pedicellate; perianth hypogynous or partly perigynous, white or cream colored to greenish or red tinged, actinomorphic, 0.5–2 cm diam.; tepals 6, often connate basally, each bearing 1 or 2, sometimes obscure to absent, yellow to green, adaxially basal nectary glands; stamens 6, anthers versatile, reniform, dehiscence transverse, extrorse or rarely introrse (Z. glaberrimus); ovary partly inferior; pistil 1, with 3 styles, tapering from ovary; stigmas 3, barely larger than diameter of style, rudimentary in staminate flowers; pedicel ascending to spreading, bracteate, bracts 2, green to red and foliaceous or white and membranous. Fruits capsular, with 3 ellipsoid, beaked sections; dehiscence septicidal, then adaxially loculicidal. Seeds 2–20 per capsule, elongate, twisted and flattened at ends. x = 8, 11, 26.

Distribution

North America including Mexico, Central America, e Asia (Japan, e Siberia).

Discussion

Species ca. 18–22 (14 in the flora).

The generic name was spelled Zigadenus by Michaux, but subsequently was often rendered as “Zygadenus,” presumably to reflect the Greek word roots more clearly. However, the original spelling has priority over that orthographic variant (W. B. Zomlefer 1997b).

As broadly circumscribed here, Zigadenus is polyphyletic (W. B. Zomlefer 1997b; W. B. Zomlefer et al. 2001) and this complex has had a complicated taxonomic and nomenclatural history (R. R. Gates 1918; O. S. Walsh 1940; S. J. Preece 1956; F. C. Schwartz 1994; W. B. Zomlefer 1997b). Numerous, variously defined segregates have been recognized, including Anticlea, Chitonia, Cyanotris, Oceanoros, Toxicoscordion, and Tracyanthus. Zigadenus shows morphological similarities to both Stenanthium (including Stenanthella Rydberg) and Amianthium.

The common name “death camas” is derived from the illness or death resulting from ingesting bulbs of Zigadenus that were mistaken for the edible ones of Camassia, an unrelated plant. Many alkaloids found in Veratrum have been isolated from most species of Zigadenus (W. B. Zomlefer 1997b; G. E. Burrows and R. J. Tyrl 2001), including zygadenine and zygacine (T. J. Gilbertson 1973; J. B. Harborne and H. Baxter 1993). All fresh parts of the plant (leaves, bulbs, flowers) are toxic. Dried parts (especially seeds and capsules) are even more potent, presumably because the alkaloids are more concentrated. Ingestion of Zigadenus by humans may result in severe illness and occasionally death even for adults. Livestock (sheep and cattle) poisoning is a serious problem in some rangeland areas of the western United States (C. D. Marsh and A. B. Clawson 1922; V. J. Tepidino 1982). Native Americans used these plants for their analgesic, antirheumatic, and emetic properties, as dermatological and orthopedic aids, and as a snake-bite remedy (D. E. Moerman 1986).

Selected References

Frame, D. M. 1999. A conspectus of Mexican Melanthiaceae including a description of new taxa of Schoenocaulon and Zigadenus. Acta Bot. Mex. 48: 27–50.

Hess, W. J. and R. C. Sivinski. 1995. A new species of Zigadenus (Liliaceae) from New Mexico, with additional comments on the section Anticlea. Sida 16: 389–400.

Preece, S. J. 1956. A Cytotaxonomic Study of the Genus Zigadenus (Liliaceae). Ph.D. dissertation. State College of Washington [Washington State University].

Schwartz, F. C. 1994. Molecular Systematics of Zigadenus Section Chitonia (Liliaceae). Ph.D. dissertation. University of Washington.

Walsh, O. S. 1940. A Systematic Study of the Genus Zigadenus Michx. Ph.D. dissertation. University of California, Berkeley.

Lower Taxa

Zigadenus brevibracteatus, Zigadenus densus, Zigadenus elegans, Zigadenus exaltatus, Zigadenus fontanus, Zigadenus fremontii, Zigadenus glaberrimus, Zigadenus micranthus, Zigadenus mogollonensis, Zigadenus nuttallii, Zigadenus paniculatus, Zigadenus vaginatus, Zigadenus venenosus, Zigadenus virescens

Key

1	Plants rhizomatous; tepals with 2 glands.	Zigadenus glaberrimus
1	Plants bulbose; tepals with 1, sometimes obscure, gland.	> 2
2	Perianth partly perigynous, tepal gland obcordate.	> 3
2	Perianth hypogynous, tepal gland obovate or obscure.	> 6
3	Perianth rotate to rotate-campanulate; pedicel erect or ascending at anthesis; tepals white or cream colored to greenish.	> 4
3	Perianth campanulate; pedicel recurved at anthesis; tepals greenish, sometimes tinged with purple.	> 5
4	Proximal stem with persistent leaf bases; tepals white.	Zigadenus vaginatus
4	Proximal stem without persistent leaf bases; tepals cream colored to greenish.	Zigadenus elegans
5	Tepals 4–6 mm.	Zigadenus virescens
5	Tepals 12–16 mm.	Zigadenus mogollonensis
6	Tepal gland obscure; tepals narrowed at base but not sharply contracted.	Zigadenus densus
6	Tepal gland prominent; inner and sometimes outer tepals strongly contracted at base into claw.	> 7
7	Bracts less than 1/2 length of corresponding pedicel; filaments thin and curved; capsules rounded, ca. 1/2 as wide as long.	Zigadenus brevibracteatus
7	Bracts 1/3–3 times length of corresponding pedicel; filaments thickened proximally and straight; capsules elongate, usually less than 1/2 as wide as long.	> 8
8	Bulbs often clumped; outer tepals often persistently reflexed below mature capsule; Sierra Nevada foothills.	Zigadenus exaltatus
8	Bulbs not clumped; outer tepals not persistently reflexed below mature capsule; elsewhere than Sierra Nevada foothills.	> 9
9	Inflorescences broad; perianth rotate.	Zigadenus fremontii
9	Inflorescences narrow, often pyramidal in early anthesis; perianth ± campanulate.	> 10
10	Filaments shorter than tepals.	Zigadenus fontanus
10	Filaments equaling or longer than tepals.	> 11
11	Distal margins of tepal gland obscure; outer tepals obtuse at apex.	Zigadenus nuttallii
11	Distal margins of tepal gland usually evident and often toothed; outer tepals often acute at apex.	> 12
12	Proximal branches of inflorescences diverging from main axis at 60°–90° when in fruit.	Zigadenus micranthus
12	Proximal branches of inflorescences diverging from main axis at 10°–60° when in fruit.	> 13
13	Inflorescences paniculate; outer tepals usually not clawed.	Zigadenus paniculatus
13	Inflorescences racemose, or paniculate with only 1 or 2 branches; outer tepals often clawed.	Zigadenus venenosus