Hymenocallis ximixtlanensis J. Jiménez Ram., Cruz Durán & E. García, sp. nov. Figs. 1, 2.

Hymenocallis ximixtlanensis is similar to H. graminifolia Greenm., but it is distinguished from it by its wider leaves (1.9–2.8 cm vs. 0.5– 0.7 cm), inflorescences with 1(–2) flowers (vs. 1–6), longer floral tubes (12–14.2 cm vs. 4 cm), larger free portion of the filaments (3.5 cm vs. 2 cm), longer anthers (2 cm vs. 1.4 cm), more ovules per locule (4 vs. 2), and its distribution in oak forest (vs. tropical deciduous forest).

TYPE:— MEXICO. Guerrero: Municipality of Atlixtac, Ximixtlán (Mezones 2), road Atlixtac-Tlatlauquitepec, 17°32’55”N, 98°52’24”W, 29 June 2013 [fl], R. Cruz et al. 9086 (holotype: FCME!; isotype: FCME!).

Herbs perennial, escapous, 23–30 cm tall. Bulbs 3.7 cm in diameter, spherical, tunicate, the cataphylls brown, membranous. Leaves 2(–3), basal, ascending, but recurved at the apical portion, 14–21(–23) × 1.9–2.2(–2.8) cm, ensiform, pale green, narrowing at base; margin entire; apex acute. Inflorescence escapous, with one flower (exceptionally 2), with bracts at the apex of the scape; scape 2.5–5 cm long, exceptionally 11–14 cm long, cylindrical, solid; bracts 4 cm long, membranous, filiform. Flowers white; tepals 7.7–9 × 0.7–0.8 cm, linear, subequal, ascending; tube of the perigonium 12–14.2 × 0.2–0.3 cm, straight, light green; staminal crown rotated, 2.6 cm high, 3.5 cm diam., crown margin briefly indented; filaments 6, the free portion 3.5 cm long, filiform, white, slightly yellowish in the last quarter, anthers ca. 2 cm long, yellow, dorsifixed and versatile; ovary 1.4–1.5 × 0.8 cm, ovoid, green, trilocular, with 4 ovules in each locule; style 18–22 cm long, dark green distally, stigma globose, dark green. Fruits and seeds unknown.

Phenology:—Flowering from June to July.

Distribution and ecology:— Hymenocallis ximixtlanensis has been localized growing in Quercus forests, at 1915 m above sea level, on limestone soil.

Etymology:—The specific epithet alludes to the site from where the only population of this species is known, the town of Ximixtlán, Municipality of Atlixtac in the Sierra Madre del Sur, Guerrero, Mexico.

Conservation:—According to the IUCN Red List categories and criteria (2022), H. ximixtlanensis is proposed as Critically Endangered (CR), because it fits with the criteria B2(a) and D, since during the exploration of the area (Municipality of Atlixtac), only a small population with less than 50 mature individuals, in an area of about 20 m ², was found.

Additional specimens examined:— MEXICO. Guerrero: Municipality of Atlixtac, Ximixtlán (Mezones 2), road Atlixtac–Tlatlauquitepec, 17°32’5”N, 98°52’24”W, 29 June 2013 [fl], R. Cruz, L.A. Alcántara & E. Hernández 9086 bis (FCME!); 21 June 2014 [fl], R. Cruz & E. Hernández 9189 (FCME!, MEXU!, UAMIZ!).