Linum rzedowskii Arreguín (1985: 262)

González-Velasco, Juan, Burgos-Hernández, Mireya, Galván-Escobedo, Iris G. & Castillo-Campos, Gonzalo, 2022, Taxonomic update of the flax family in Mexico, Phytotaxa 549 (2), pp. 141-184 : 169-170

Linum rzedowskii Arreguín (1985: 262) . ( Fig. 10a ).

Type:— MEXICO, State of Mexico: Llano Pinahua , approximately 8 km SW from Rio Frío , municipality of Ixtapaluca , 3200 m, in a clearing in the middle of the pine forest, J. Rzedowski 37285 (holotype ENCB!) .

Description: — Herbs, perennial, 15–25 cm in height, glabrous, root thick; stem creeping or prostrate, slightly striate, branched from the base, glabrous. Leaves entire, alternate, linear-lanceolate, (3.0–)4.6–5.5(–10.0) × (1.0–)1.1–1.3(– 2.0) mm, sessile, apex acuminate; 1–3-nerved, central nerve evident; coriaceous, glabrous, stipular glands absent. Inflorescence racemose, pedicels (4.5) 6.9–10.6 mm long, glabrous; bracts 2.1–4.2 mm long, margin entire, apex acute, stipular glands absent; sepals persistent, ovate, 3.0–4.0 × 2.0–3.0 mm, shorter than the capsule; margin white, scariose; apex acute; 1-3 nerved, barely evident lateral nerves; glabrous, stipular glands absent; petals blue, obovate, 6.0–8.0(11) mm long, glabrous; stamens 2.4–4.2 mm long; anthers 0.6–1.0 mm long, yellow; staminodia minute; styles free, 1.1–1.9 mm long; stigmata capitate, yellow. Fruit ovate, yellow, 5.0–6.0 × 4.0–5.0 mm, glabrous, pericarp thick, apex acute, dehiscent into 10 segments; septa ciliate; seeds elliptical, brown, 3.0–4.0 × 1.2–1.5 mm.

Distribution: —Endemic to Mexico, in the State of Mexico ( Fig. 5b ).

Habitat and ecology: —Grasslands, pine forests, low deciduous tropical forest. Elevation 3000–3500 m.Andosol, Cambisol, Phaeozem, Planosol, Regosol, and Vertisol soil types.

Phenology: —Flowering and fruiting in July–August.

Note: —This blue-flowered species occurs only in a small area of the State of Mexico; its distribution does not overlap that of L. lewisii . The creeping habit, the white margins of sepals, and the size of petals support an easy differentiation.

Conservation status: —Although, according to the B1 criterion established by the IUCN, L. rzedowskii can be considered Critically Endangered (CN) (EOO = 24 km 2), due to its AOO of 24 km 2 and a number of known localities, together with the degradation of its habitat adjacent to the largest human population nuclei by deforestation and tourism ( Pineda-Jaimes et al. 2009, CONABIO 2021), this species is considered EN (B1 + 2abc(iii)).

Specimens examined: — MEXICO. State of Mexico: Chalco, Río Frío Estación Forestal Zoquiapan , 3500 m, 16 August 1974, E. García M. et al. 1256 ( CHAPA!) ; Ixtapaluca, Estación Experimental de Investigación y Enseñanza de Zoquiapan 8 km al S de Río Frío, 3250 m, 04 July 1975, S.D. Koch 75289 (CHAP!, CHAPA!) ; Ixtapaluca, Estación Experimental de Investigación y Enseñanza de Zoquiapan 8 km al S de Río Frío, 3000 m, 28 August 1975, S.D. Koch & J. Magaña M. 75471 ( CHAPA!) ; Ixtapaluca, Estación Experimental de Investigación y Enseñanza de Zoquiapan 8 km al S de Río Frío, 3200 m, 30 October 1975, S.D. Koch 75704 ( CHAPA!) ; Ixtapaluca, Estación Experimental de Investigación y Enseñanza de Zoquiapan 8 km al S de Río Frío, 3200 m, 3 July 1978, R. Vega A. 229 ( CHAPA!) ; Ixtapaluca, Llano Pinahua , 3250 m, 12 August 1980, Rzedowski 36790 (CIIDIR!, IEB!, SLPM!) ; Ixtapaluca, Llano Grande , 3000 m, 30/August/1983, E. Ventura V. 1295 (IEB!, XAL!) ; Ixtapaluca, Llano Tepochaico , 3350 m, 17/July/1983, Rzedowski 38109 (IEB!, XAL!) ; Ixtapaluca, Llano Grande , 3100 m, 3 July 1983, E. Ventura V. 1051 ( UAMIZ!) .

Figures

FIGURE 5. Geographic distribution in the Mexican territory of:A. L. cruciata, L. lasiocarpum, L. lewisii, L. mexicanum, and L. tenellum; B. L. elongatum, L. neomexicanum, L. puberulum, L. rzedowskii, and L. schiedeanum; C. L. modestum, L. orizabae, L. pringlei, L. scabrellum, and L. vernale. Maps by Ma. Isabel Olivares.

FIGURE 10. A. Linum rzedowskii; B. Linum schiedeanum; C. Linum tenellum; D. Linum usitatissimum. Photographs by José Luis Colin.