Eryngium monocephalum Cav.

Eryngium monocephalum Cav. Anal. Hist. Nat. 2: 116. 1800
Eryngium bromeliaefolium Delar. f. Eryng. 60. 1808. ? Eryngium axilliflorum Turcz. Bull. Soc. Nat. Mosc. 20 1 : 172. 1847. Eryngium alternalum Coult. & Rose, Contr. U. S. Nat. Herb. 3: 298. 1895. Eryngium involucratum Coult. & Rose, Contr. U. S. Nat. Herb. 3: 299. 1895. Eryngium grande Hemsl. & Rose; Rose, Contr. U. S. Nat. Herb. 8: 332. 1905.
Stout, caulescent, glabrous perennials, 6-30 dm. high, from a short woody caudex bearing a fascicle of fleshy-fibrous roots, the stems solitary, erect, branching; basal leaves linearlanceolate, 1-6 dm. long, 6-25 mm. broad, slightly narrowed at the base, acuminate at the apex, spinose-serrate with divergent or spreading teeth 5-30 mm. long, often replaced by slender spines toward the base, axillary and intermediate spines usually present, the venation parallel; sheaths nearly as broad as the blades, plane, 1-3 cm. long; cauline leaves like the basal, alternate, the upper opposite, amplexicaul, vaginate and mostly recurved; inflorescence sparingly cymosely branched or the branching entirely suppressed, the heads large, solitary to few, pedunculate, the flowers very numerous; heads ovoid, 1-2.5 cm. long, 1-1.5 cm. broad; bracts 12-30, biseriate, rigid, spreading-ascending, strongly imbricate, linear to linear-lanceolate, 3-S cm. long, 3-12 mm. broad, pungent, entire or spinose-serrate, exceeding and often enclosing the heads (or rarely conspicuously shorter than the heads); bractlets lanceolatesubulate, 4-7 mm. long, pungent, entire, slightly exceeding the fruit; coma wanting; sepals lanceolate to ovate, 2-4 mm. long, obtuse, mucronate; petals oblanceolate, 2-3 mm. long; styles short but slightly exceeding the sepals; fruit cuneate-cylindric, 3-5 (or 8?) mm. long, the lateral scales forming two incised wings, the calycine few, the surfaces naked or nearly so.
Type locality: "Huanajuato [Guanajuato] and Chilpancingo. New Spain," collector unknown. Distribution: Hidalgo to Morelos and Oaxaca (Pringle 10,245, Pur pits 3747).