Linum species, 1753

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 : 146-147

Key to Linum species in Mexico

1. Fruit dehiscent into 5 segments ..........................................................................................................................................................2

- Fruit dehiscent into 10 segments ........................................................................................................................................................8

2. Corolla yellow ....................................................................................................................................................................................3

- Corolla yellow-orange to salmon with a red to wine-red base...........................................................................................................5

3. Root thin; stem puberulent at the base; fruit ovoid ............................................................................................................................4

-. Root thick; stem glabrous; fruit ellipsoid ........................................................................................................................ L. aristatum

4. Stipular glands absent, sometimes present only in some parts, then barely conspicuous.................................................. L. australe

- Stipular glands present throughout the plant, very conspicuous .......................................................... L. australe var. glandulosum

5. Stems pilose locally or throughout .....................................................................................................................................................6

-. Stems glabrous throughout .................................................................................................................................................................7

6. Plant hirsutulose at the base; sepals glabrous; fruit with translucent thin pericarp............................... L. berlandieri var. filifolium

- Plant densely gray-puberulent to the inflorescence; sepals pubescent; fruit with thick opaque pericarp ..................... L. puberulum

7. Basal leaves alternate; sepals deciduous, 3-nerved; anthers brick-red........................................................................... L. elongatum

-. Basal leaves opposite; sepals persistent, 1-nerved; anthers brown ..................................................................................... L. vernale

8. Corolla blue ........................................................................................................................................................................................9

- Corolla yellow, yellow-orange, white, or pink .................................................................................................................................11

9. Stems erect or ascending ..................................................................................................................................................................10

- Stems creeping or prostrate ............................................................................................................................................ L. rzedowskii

10. Pedicels villous; anthers white; stigmata capitate ................................................................................................................. L. lewisii

- Pedicels glabrous; anthers bright-yellow; stigmata linear to claviform ................................................................... L. usitatissimum

11. Plants densely pubescent throughout................................................................................................................................................12

- Plants glabrous or locally pubescent ................................................................................................................................................13

12. Basal leaves opposite; bracts with stipular glands, conspicuous; petals yellow-orange, pilose at the base.................. L. scabrellum

- Basal leaves in whorls; upper bracts without stipular glands; petals yellow, glabrous..................................................... L. tenellum

13. Stems decumbent..............................................................................................................................................................................14

- Stems erect........................................................................................................................................................................................15

14. Leaves widely ovate or elliptical, scariose; anthers 0.7–1.2 mm long............................................................................... L. cruciata

- Leaves narrowly oblanceolate, obovate to narrowly elliptical, rough; anthers 0.5 mm long...................................... L. lasiocarpum

15. Annual herbs.....................................................................................................................................................................................16

- Perennial herbs .................................................................................................................................................................................17

16. Basal leaves in whorls, obovate; 3-nerved sepals; styles fused to near the apex; fruit pale-yellow throughout............... L. longipes

- Basal leaves opposite, elliptical-oblanceolate; 1-nerved sepals; styles free; fruit yellow with purple hues on the upper portion ...... ................................................................................................................................................................................ L. neomexicanum

17. Root thick .........................................................................................................................................................................................18

- Root thin ...........................................................................................................................................................................................20

18. Basal leaves opposite or in whorls; stigmata light brown; fruit yellow with purple hues at the upper portion ...............................19

- Basal leaves alternate; stigmata yellow; fruit yellow throughout ................................................................................... L. flagellare

19. Styles free or connate at the base ...................................................................................................................................... L. orizabae

- Styles fused to half or close to the apex ....................................................................................................................... L. mexicanum

20. Fruit glabrous....................................................................................................................................................................................21

- Fruit pubescent at the apex ................................................................................................................................................. L. nelsonii

21. Fruit yellow with purple hues at the upper portion; petals white or pink........................................................................... L. pringlei

- Fruit yellow throughout; petals yellow to greenish-yellow..............................................................................................................22

22. Basal leaves alternate or opposite....................................................................................................................................... L. rupestre

- Basal leaves in whorls ......................................................................................................................................................................23

23. Leaves with stipular glands at the base; pedicels 0.1–0.2 mm long; bracts 2.0–3.0 mm long; sepals 2.0–5.0 × 1.0– 1.5 mm, seeds reddish-brown............................................................................................................................................................ L. schiedeanum

- Leaves without stipular glands at the base; pedicels 3.5–14.7 mm long; bracts 0.6–1.1 mm long; sepals (1.2)1.7–1.8 × 0.5–0.7 mm; seeds light brown.................................................................................................................................................... L. modestum