Note 864 — BOOK XIII. THE NATURAL HISTORY OF EXOTIC TREES, AND AN ACCOUNT OF UNGUENTS.
John Bostock translation
The sap of the elm leaves a saline deposit on the bark, principally formed of carbonate of potassa. Fée is at a loss to know whether Pliny here alludes to this or to the manna which is incidentally formed by certain insects on some trees and reeds. But, as he justly says, would Pliny say of the latter that it is “ad nihil utile”—“good for nothing”?