Epilobium L.

Luo, Yike & Xie, Lei, 2023, A checklist of Onagraceae in the Pan-Himalaya region, Phytotaxa 597 (4), pp. 245-268 : 252-254

3. Epilobium L. , pro parte.

Lectotype (designated by Britton & Brown 1913):— Epilobium hirsutum Linnaeus (1753: 347) .

Herbs perennial or annual, erect to ascending or decumbent, with leafy rosettes, stolons, soboles, or turions. Stems glabrous to pubescent, some species with 2–4-lines of strigillose decurrent from margins of petioles. Leaves subsessile to petiolate, opposite and decussate, becoming alternate and in inflorescence; lanceolate to ovate, sometimes to sublinear. Flowers 4-merous, actinomorphic or rarely zygomorphic, with floral tube, the base of style has nectar; petals rose-purple to white, obcordate or obtrullate, apically notched; stamens 8, in two unequal series; ovary with 4 locules, stigma erect, entire or deeply 4-lobed. Fruit pedicellate or sessile, 4-loculed. Seeds with coma. Chromosome number: 2n = 36 ( Chen et al. 1992).

The genus Epilobium is the largest one in the family, comprising 165 species (185 taxa) ( Wagner et al. 2007). The monophyly of the strictly defined Epilobium (with exclusion of Chamaenerion ) was strongly supported (100% BS) by analyses of the nrITS region ( Baum et al. 1994) and nrITS plus trn L-F regions ( Levin et al. 2003). It was divided into eight sections according to the new classifications ( Wagner et al. 2007). In the Pan-Himalaya region, there are 35 species (37 taxa) of Epilobium , all of which are in the same section (E. sect. Epilobium ).

Key to species of Epilobium in the Pan-Himalaya region

1 Stigma deeply 4-lobed........................................................................................................................................................................2

- Stigma entire or shallowly emarginate ...............................................................................................................................................5

2 Stems with long spreading villous pubescent and short erect glandular hairs ...................................................................................3

- Stems strigillose, without long villous pubescent ..............................................................................................................................4

3 Petals (7–) 10–20 mm; stigma exserted beyond anthers ........................................................................................... 3.13. E. hirsutum

- Petals 5–8 mm; stigma surrounded by anthers .................................................................................................... 3.22. E. parviflorum

4 Petals 5–7.5 mm; leaves obovate to oblanceolate ............................................................................................................3.3. E. blinii

- Petals 6–8 mm; leaves lanceolate-linear.................................................................................................................. 3.28. E. staintonii

5 Stem with densely strigillose throughout ..........................................................................................................................................6

- Stem glabrous, with strigillose lines on internodes, decurrent from margins of petioles, sometimes lines not obvious .................16

6 Leaves narrowly lanceolate to sublinear, or lanceolate-elliptic, length is more than 5 times the width ............................................7

- Leaves elliptic to ovate (or short lanceolate), length is less than 5 times the width ..........................................................................9

7 Leaves margin denticulate .......................................................................................................................... 3.23. E. platystigmatosum

- Leaves margin subentire.....................................................................................................................................................................8

8 Leaves lanceolate-elliptic to lanceolate-oblong; petals white, 3–4(–4.7) mm; coma tawny.................... 3.10. E. fastigiatoramosum

- Leaves sublinear to narrowly lanceolate; petals white to pink, 3–7(–9) mm; coma white or rarely tawny.............. 3.20. E. palustre

9 Flower 7–16 mm ...............................................................................................................................................................................10

- Flower 3–7.2 mm ..............................................................................................................................................................................12

10 Stem densely appressed-tomentose, sometimes mixed with glandular hairs on inflorescence..............................3.21. E. pannosum

- Stem densely glandular and strigillose throughout ..........................................................................................................................11

11 Leaves margin sharply serrulate with 28–42(–60) teeth; capsules 7–11 cm ........................................................... 3.15. E. kermodei

- Leaves margins more or less sharply denticulate with 7–22 teeth; capsules 3.5–7 cm long..................................3.4. E. brevifolium

12 Stems with brown basal scales .........................................................................................................................................................13

- Stems without brown basal scales ....................................................................................................................................................15

13 Stems mostly shorter than 20 cm; leaves apex acute, subsessile .....................................................................................................14

- Stem 15–40 cm; leaves apex subobtuse or acute, petiole 1–4 mm .................................................................................3.9. E. fangii

14 Upper internodes elongate, exceeding 3 times leaf length .................................................................................... 3.7. E. clarkeanum

- Internodes subequal, slightly longer than leaves..............................................................................................3.32. E. trichophyllum

15 Petals 3–4.3 mm ................................................................................................................................................ 3.19. E. minutiflorum

- Petals 5–7.2 mm .................................................................................................................................................... 3.25. E. royleanum

16 Petiole obvious more than 2 mm ......................................................................................................................................................17

- Leaves subsessile, or only about 2mm in the lower part of the plant...............................................................................................22

17 Leaves often crowded and spirally arranged on mid-stem......................................................................................... 3.27. E. sinense

- Leaves opposite below inflorescence ...............................................................................................................................................18

18 Stems 13–100 cm tall .......................................................................................................................................................................19

- Stems shorter than 35 cm .................................................................................................................................................................21

19 Petals 3–8 mm ..................................................................................................................................................................................20

- Petals 10–11 mm ....................................................................................................................................................... 3.14. E. indicum

20 Leaves margin serrulate with 15–35 teeth per side, lanceolate to narrowly ovate; seeds 1.1–1.3 mm .................. 3.31. E. tibetanum

- Leaves margin densely serrulate with (20–)30–50 teeth per side, narrowly lanceolate to sublinear; seeds 0.8–1 mm ....................... ............................................................................................................................................................................... 3.8. E. cylindricum

21 Underground stems with brown coriaceous scales.................................................................................................. 3.1. E. aitchisonii

- Stems base with stolons, without scales ................................................................................................................ 3.34. E. wattianum

22 Plants completely glabrous, and strigillose lines is absent.................................................................................. 3.18. E. leiophyllum

- Stem glabrous, with (2 or)4 raised strigillose lines on internodes ...................................................................................................23

23 Stem with brown coriaceous scales..................................................................................................................................................24

- Stem without brown coriaceous scales.............................................................................................................................................32

24 Flower 6–14 mm ...............................................................................................................................................................................25

- Flower less than 3.5–6.5 mm ............................................................................................................................................................29

25 Herbs with soboles ...........................................................................................................................................................................26

- Herbs with fleshy turion ...................................................................................................................................................................27

26 Seeds gray-brown, 1–1.3 mm ................................................................................................................................3.26. E. sikkimense

- Seeds dark brown, 1.4–1.6 mm ............................................................................................................................... 3.16. E. kingdonii

27 Leaves alternate above, margin sharply denticulate.........................................................................................................................28

- Leaves nearly all opposite, obscurely serrulate......................................................................................................... 3.11. E. glaciale

28 Leaves ovate, 2–7×1.2–2.6........................................................................................................................................... 3.17. E. laxum

- Leaves subleathery, narrowly ovate to lanceolate, 1.5–5.5×0.5–1.5 ................................................................3.30. E. subcoriaceum

29 Stigma clavate to subcapitate ......................................................................................................................................3.12. E. gouldii

- Stigma capitate .................................................................................................................................................................................30

30 Stem often well branched from the base, a dense tuft of coriaceous brown scales..........................................................................31

- Stem usually unbranched from the base, and the scales sparse......................................................................3.5. E. brevisquamatum

31 Pubescence of inflorescence with a conspicuous admixture of glandular hairs..................................................... 3.35. E. williamsii

- Pubescence of inflorescence entirely strigose ........................................................................................................ 3.6. E. chitralense

32 Stigma capitate to broadly clavate....................................................................................................................................................33

- Stigma clavate .................................................................................................................................................3.29. E. stracheyanum

33 Stem somewhat 4-angled, with (2 or)4 raised strigillose lines on internodes .................................................. 3.33. E. wallichianum - Stem with 2 raised strigillose lines on internodes ............................................................................................................................34

34 Herb erect, with leafy basal soboles, elongated rosettes, or rarely fleshy stolons; stigma capitate or broadly capitate ...................... ...................................................................................................................................................................................3.2. E. amurense

- Herb with turion; stigma capitate to broadly clavate...................................................................................3.24. E. rhynchospermum