Each leaf has a slender stem-like axis, which twines round a support and bears leaflets at intervals; it goes on growing indefinitely.
Elsewhere and also earlier, the serpent twines round three heads.
The best known kind is S. heterophylla, and of this there is a distinct narrow-leaved form angustifolia, which twines less freely.
When a sensitive tendril comes into contact with a foreign body, its growth becomes so modified that it twines round it.