These fragile leaves and stems were those originally used by the French in their Julienne soup, according to Auguste Kettner.
Wood sorrel is less acid than field sorrel.
It appears in the soup as little 'threads,' these being the stalks, the trefoil leaves having dissolved. They are the origin of the fact that a Julienne soup should contain little vegetable slithers finely cut and hence of the phrase en julienne. In his day a polished brass cannon ball was sometimes used as pestle. Field sorrel is well worth growing in the garden when woods and fields are far away.