Taxonomic update of the flax family in Mexico Author González-Velasco, Juan 0000-0001-8743-3906 Departamento de Botánica, Colegio de Postgraduados. km 36.5 carretera México-Texcoco, Montecillo, 56230 Texcoco, Mexico, Mexico. & gonzalez. juan @ colpos. mx; https: // orcid. org / 0000 - 0001 - 8743 - 3906 gonzalez.juan@colpos.mx Author Burgos-Hernández, Mireya 0000-0003-3036-297X Departamento de Botánica, Colegio de Postgraduados. km 36.5 carretera México-Texcoco, Montecillo, 56230 Texcoco, Mexico, Mexico. & burgos. mireya @ colpos. mx; https: // orcid. org / 0000 - 0003 - 3036 - 297 X burgos.mireya@colpos.mx Author Galván-Escobedo, Iris G. 0000-0003-4250-4971 Departamento de Botánica, Colegio de Postgraduados. km 36.5 carretera México-Texcoco, Montecillo, 56230 Texcoco, Mexico, Mexico. & igalvan @ colpos. mx; https: // orcid. org / 0000 - 0003 - 4250 - 4971 igalvan@colpos.mx Author Castillo-Campos, Gonzalo 0000-0002-3059-8109 Red de Biodiversidad y Sistemática. Instituto de Ecología A. C. Carretera antigua a Coatepec km. 351, El Haya, 91073, Xalapa, Veracruz, Mexico. & gonzalo. castillo @ inecol. mx; https: // orcid. org / 0000 - 0002 - 3059 - 8109 gonzalo.castillo@inecol.mx text Phytotaxa 2022 2022-06-08 549 2 141 184 journal article 67684 10.11646/phytotaxa.549.2.3 62e44cf6-6f9d-4658-a89b-a0ddf687b5b9 1179-3163 6622753 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 !) . FIGURE 10. A. Linum rzedowskii ; B. Linum schiedeanum ; C. Linum tenellum ; D. Linum usitatissimum . Photographs by José Luis Colin. 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 !) .