Lythrum L.

1. Lythrum L. View in CoL 3

(Inch Peplis L. and Middendorfia Trautv. )

Annual or perennial; leaves alternate, opposite or whorled. Flowers usually 6-merous (sometimes 4- or 5-merous), usually solitary in the leaf-axils, sometimes in pairs or in small, whorllike cymes, which may form terminal spikes; each flower shortly pedicellate, with 2 bracteoles. Hypanthium usually tubular, sometimes short and wide. Epicalyx present. Petals usually

present. Stamens 2-12. Capsule usually septicidally dehiscent with 2 valves, rarely dehiscing irregularly or by 4 apical teeth.

In several species the flowers are trimorphically heterostylous, with the stamens in two series of different length, and the stigma at a level below the anthers of both series, or above them both, or between the two.

Literature: J. Borja Carbonell, Anal. Inst. Bot. Cavanilles 23:

145-62 (1968).

1 Flowers trimorphically heterostylous; stamens 12, at least some of them exceeding the sepals

2 Flowersmostlyinterminalspikescomposedofwhorl-like cymes of 4 or more; petals at least 7 mm

3 Leavestruncateorroundedat thebase,usuallyhairy; epicalyx-segments much longer than the sepals 1. salicaria

3 Leaves conspicuously cuneate at the base, glabrous; epicalyx-segments about equalling the sepals 2. virgatum

2 Flowers solitary, rarely in pairs; petals not more than 6 mm

4 Fruiting hypanthium cylindrical, or somewhat dilated at the obtuse base 6. flexuosum

4 Fruitinghypanthiumobconical,taperedgraduallyto a narrow base

5 Usually perennial; hypanthium red-spotted near the base, usually shorter than subtending leaf 3. junceum

5 Annual; hypanthium green, or entirely red at the base, but not spotted, often longer than the subtending leaf

6 Hypanthium with 6 narrow, keel-like ridges decurrent from base of epicalyx-segments, which are about twice as long as sepals 4. acutangulum

6 Hypanthium without conspicuous ridges; epicalyx-segments about half as long as sepals 5. castellanum

1 Flowers homostylous; stamens usually less than 12, not exceeding the sepalsand usually included in the hypanthial tube

7 Tubeofhypanthium pelviform tobroadlycampanulatein fruit, scarcely longer than wide; capsule ± globose

8 Leaveslinear-oblanceolateto linear,mostly4-7 timesas long as wide; epicalyx-segments and sepals longer than hypanthial tube 13. volgense

8 Leaves orbicular to oblong-lanceolate, mostly 1-3 times as long as wide; epicalyx-segments and sepals usually shorter than hypanthial tube 9 Tube of hypanthium hemispherical to pelviform in fruit,

shorter than the capsule; plant glabrous; stems extensively creeping and rooting 12. portala 9 Tube of hypanthium broadly campanulate in fruit, at least as long as the capsule; plant often scabrid, at least in younger parts; stems ±erect, scarcely rooting

11. borysthenicum 7 Tube of hypanthium cylindrical or narrowly campanulate in fruit, distinctly longer than wide; capsule usually ellipsoid or cylindrical 10 Leaves oblong-lanceolate to broadly obovate, all widest above the middle and most of them less than 2-5 times as long as wide 11. borysthenicum 10 Leaves linear to oblong, rarely somewhat oblanceolate,

usually parallel-sided or widest near the middle, most of them more than 2-5 times as long as wide 11 Style c. 0-25 mm; hypanthium in fruit less than twice as long as wide 10. thesioides 11 Style 1-5-2 mm; hypanthium in fruit 3-6 times as long as wide 12 Epicalyx-segments less than 0-5 mm, triangular, about equalling the sepals, involute in fruit 9. tribracteatum 12 Epicalyx-segments at least 1 mm, subulate, longer than the sepals, erect or patent in fruit

13 Flowers (5-)6-merous; stamens (2—)4—6(—12); leaves mostly more than 2 mm wide 7. hyssopifolia

13 Flowers 4(-5)-merous; stamens 2-3; leaves mostly less than 2 mm wide 8. thymifolia