Ruppia

De Castro, O., Geraci, A., Mannino, A. M., Mormile, N., Santangelo, A. & Troia, A. 2021: A contribution to the characterization of Ruppia drepanensis (Ruppiaceae), a key species of threatened Mediterranean wetlands. – Ann. Missouri Bot. Gard. 106: 1-9

but modified

1	Fruiting peduncles straight or twisted; leaves 0.2-0.3 mm wide Ruppia maritima
1'	Fruiting peduncles laxly to densely spirally coiled 2
2	Fruiting peduncles laxly spirally coiled; leaves 0.5-1.2 mm wide Ruppia spiralis
2'	Fruiting peduncles densely spirally coiled; leaves 0.1-0.2 mm wide Ruppia drepanensis