Dodders are parasitic plants. They don't have roots nor leaves, and their thin stems garland around their host plants. And they suck the saps of those. Let's call this one 'Beggar's Ticks Dodder' (Cuscuta scandens) because it often seems to grow on Beggar's Ticks (Bidens frondosa).
It is considered as an invasive plant, like the plant it has chosen to grow on here, for that matter. The Japanese Knotweed (Reynoutria japonica), with its big leaves is a serious pest in many parts of France.'Beggar's Ticks Dodder' is still quite uncommon in Perigord, but its numbers are increasing. It grows in some places on the Dordogne banks, and the river helps it to go elsewhere.
Many little white flowers will give many round seeds.