Field Bindweed, Convolvulus arvensis
The thin supple stems of this weed of cultivation
twine around grasses and other plants which it
depends on for support. Both the thickness of
the stem and the diameter of the spiral scarcely
change as the plant grows, so the spiral would
fit neatly inside a cylinder.
A spiral or screw of this kind can be generated
mathematically by rotating a point in the X,Y
plane through a circle, while advancing it
steadily in the Z direction.