Lythrum

Meikle, R.D. 1977: Flora of Cyprus 1
but modified
1Petals c. 6 mm long, conspicuous; stamens 12, some of them usually exserted, leaves shortly and bluntly auriculate at base; perennial
1'Petals usually less than 3 mm long, inconspicuous; stamens (1-)2-6(-8), included; leaves not auriculate at base; annual, rarely perennial
2Lobes of epicalyx narrowly deltoid, much longer than the sepals; leaves linear or narrowly oblong
2'Lobes of epicalyx minute, bluntly deltoid, rather shorter than the sepals; leaves narrowly ovate, obovate or oblong