Linum tenellum Chamisso & Schlechtendal (1830b: 235)

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 : 174-175

Linum tenellum Chamisso & Schlechtendal (1830b: 235) . ( Fig. 10c ).

Type:— MEXICO. Veracruz: Near Jalapa, C. J. W. Schiede & F. Deppe 518 (holotype HAL!, syntype HAL!, WU) .

Cathartolinum tenellum Small (1907e: 77) .

Description: — Herbs, annual, occasionally perennial, 8–50 cm in height, densely pubescent; hairs whitish, conspicuous; root thin; stems erect to decumbent, striate, commonly unbranched up to the inflorescence, pubescent. Leaves glandulardentate; basal leaves arranged in whorls of 4; distal leaves alternate, rarely opposite; elliptical to obovate toward the base, lanceolate to oblanceolate or oblong toward the distal part; 3.0–13.0 × (1.4)1.5–5.0 mm, gradually decreasing toward the inflorescence; sessile, apex acute to obtuse, 1-nerved; slightly membranous, pubescent; stipular glands present at the base. Inflorescence a cymose panicle, sparsely branched; pedicels 2.0–10.0 mm long; bracts 2.1–3.4 mm long, pubescent, margin glandular-dentate, apex acute, stipular glands present at the base of the lower bracts; sepals persistent, lanceolate to ovate, 1.9–3.0 × (0.8) 1.2–1.5 mm, margin glandular-dentate, apex acute, 3-nerved, pubescent or only along veins, stipular glands absent; petals yellow, obovate, 2.0–6.0 mm long, glabrous; stamens 2.0–3.0 mm long, sparsely pubescent at the base; anthers up to 1 mm long, light yellow; staminodia present, occasionally absent; styles free, 1.7–2.5 mm long; stigmata capitate, light yellow. Fruit ovoid, yellow with purple hues on the upper portion, 1.5–3.0 × 1.2–1.8 mm, sparsely pubescent, apex acute, puberulent or glabrous, dehiscent into 10 segments, false septa incompletely developed, septa without marginal cilia; seeds elliptical or ovate, brown, 1.0–1.2 × 0.5–0.7 mm.

Distribution: —Endemic to Mexico, in Chiapas, Queretaro, San Luis Potosi, Tamaulipas, and Veracruz ( Fig. 5a ).

Habitat and ecology: —Deciduous forest, oak forests, oak-pine forests, grasslands, and high or medium subevergreen tropical forest. Elevation 750–2200 m. Andosol, Cambisol, Phaeozem, Lithosol, Luvisol, Regosol, Vertisol, and Xerosol soil types.

Phenology:—Flowering and fruiting in April–December.

Note: — Linum tenellum is the only species in the genus that has leaves in whorls and that is densely pubescent throughout, with more stiff and conspicuous hairs, these being characters that support an accurate identification.

Conservation status: —According to the IUCN criteria ( IUCN 2019), L. tenellum is VU (B1 + 2ac(iii)). This species has an EOO of 6,180,759 km 2 and an AOO of 28 km 2, and is known from <10 localities. Additionally, the species has a restricted distribution to the Sierra Madre Oriental. Rzedowski & Calderón de Rzedowski (1992) mentioned L. tenellum as a species in danger of extinction.

Specimens examined: — MEXICO. Chiapas: La Independencia, Lake shore of Montebello , 1588 m, 16°06’16.81”N, 91°41’23.2”W, 2 May 1945, A.J. Sharp 45453 ( MEXU!) . Queretaro: Arroyo Seco, Aprox. 3 km de San Juan Buenaventura, 1460 m, 8 December 1988, E. Carranza 1236 ( IEB!) ; Landa, 2 km al SO del Madroño , 1720 m, 8 May 1989, E. González 550 (IEB!, MEXU!) . San Luis Potosi: Rioverde , Parque Nacional El Potosí, 2187 m, 1 March 2018, A.K. Gudiño-Cano et al. 646 (SLPM) . Tamaulipas: Piedra Iman, 2 km al ESE de Sn. José, Sierra Sn. Carlos , 790 m, 24°40’30”N, 90°06’00”W, 22 November 1984, O. Briones 1245 ( ANSM!) . Veracruz: Atzalan , La Florida, 1700 m, 2 April 1976, F. Ventura A. 12609 (SLPM!, XAL!) ; Coacoatzintla, Coacoatzintla , 1200 m, 14 May 1973, F. Ventura A. 8294 (IEB!, XAL!) ; Miahuatlán , 5 km al SE de la Colonia Reforma, 1750 m, 19°43’00”N, 56°51’00”W, 24 April 1979, J.I. Calzada 5331 ( XAL!) ; Tonayan, Desviación de Tonayán , 1600 m, 1 June 1981, M. Chazaro B. 156 ( XAL!) .

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.