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Flora of Australia Online

EPILOBIUM

Joy Thompson

Epilobium L., Sp. Pl. 1: 347 (1753), Gen. Pl. 5th edn, 164 (1754); from the Greek epi (upon), and lobos (pod), referring to the epigynous flowers.
Willowherb.

Type: Epilobium hirsutum L.

Perennial or rarely annual herbs, sometimes woody at base. Leaves opposite or alternate. Flowers solitary in upper leaf axils, usually actinomorphic; without bracteoles. Hypanthium short but evident or (not in Australia) absent or to 4 cm long. Sepals 4, deciduous. Petals 4, usually white, pink or purplish pink, or (not in Australia) yellow or red. Stamens 8. Ovary 4-locular. Fruit a slender, elongate capsule. Seeds numerous, occasionally (not in Australia) few, usually with a coma of long, fine hairs. n = 18, pers. comm. P.C.Hoch et al. , Missouri Botanical Garden. 

A genus of c. 165 species, widespread throughout the world especially in high latitudes and at high altitudes; 15 species in Australia of which 11 are native (5 endemic) and four naturalised. 

Hybrids between many species of Epilobium are common.

The author accepts the opinion given by P.H.Raven and T.E.Raven (D.S.I.R. Bull. 87 (1976)) and endorsed by P.Hoch, Associate Curator, Missouri Botanical Garden, pers. comm., 1989, that the formae listed by Haussknecht (Monogr. Epilobium, Jena (1884)) were not intended as formal taxonomic entities. She considers these names to have been used only to assist discussion of an observed range of variation, and their publication to be invalid. However, as this opinion is not unanimous among authorities, these names have been included in this treatment.

H.C.Haussknecht, Monogr. Epilobium, Jena (1884); P.H.Raven & T.E.Raven, The Genus Epilobium in Australasia, D.S.I.R. Bull. 216 (1976); P.H.Raven, Generic and Sectional delimitation in Onagraceae, Tribe Epilobieae, Ann. Missouri Bot. Gard. 63: 326 (1976); K.R.West & P.H.Raven, New Zealand J. Bot. 15: 503–509 (1977).

1 Plant erect

2

1: Plant low-growing, usually mat-forming

10

2 Seeds with a pale cellular rim

gunnianum

2: Seeds without a pale rim

3

3 Stems with conspicuous long, spreading non-glandular hairs

hirtigerum

3: Stems without conspicuous long, spreading non-glandular hairs, if spreading the pubescence glandular

4

4 Leaves little if at all longer than wide; seeds 0.5–0.7 mm long

rotundifolium

4: Leaves much longer than wide; seeds longer than 0.7 mm

5

5 Inner surface of hypanthium glabrous; fruiting pedicels 1.5–5 cm long

sarmentaceum

5: Inner surface of hypanthium pubescent; fruiting pedicels usually less than 3 cm long

6

6 Seeds finely but conspicuously striate, very narrowly obovoid; petals to 5.5 mm long

ciliatum

6: Seeds not conspicuously striate or if somewhat striate then obovoid; petals more or less than 5.5 mm long

7

7 Glandular hairs restricted to the hypanthium

obscurum

7: Glandular hairs absent, or if present not restricted to the hypanthium

8

8 Leaf bases decurrent, forming ridges on the stem

tetragonum

8: Leaf bases not decurrent

9

9 Glandular hairs absent from the flowering region; leaves narrowly lanceolate to lanceolate; inflorescence nodding

pallidiflorum

9: Glandular hairs present in the flowering region or, if absent, the leaves narrowly ovate to ovate; inflorescence erect

billardierianum

10 Seeds with a pale cellular rim

11

10: Seeds without a pale rim

12

11 Coma absent

curtisiae

11: Coma present

willisii

12 Leaves of the flowering region alternate

13

12: Leaves of the flowering region opposite

14

13 Petals purplish-pink; fruiting pedicels pubescent; seeds 1.3–1.4 mm long

fugitivum

13: Petals white; fruiting pedicels usually glabrous; seeds 0.8–0.9 mm long

tasmanicum

14 Stems variously hairy

brunnescens

14: Stems glabrous or almost so

perpusillum

15 Naturalised since publication of the Flora of Australia treatment

hirsutum

 

Data derived from Flora of Australia Volume 18 (1990), a product of ABRS, ©Commonwealth of Australia