Nettle
2 of the 6 encyclopedias on this shelf carry an entry for Nettle. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
an herb belonging to the same family as the elm, hemp, and hop vine. In the popular mind nettles are associated with their sting, but that is not their only characteristic. The fibre of several species is used for ropes, cloth, and lace. The fruit is used like hops in making beer. Nettle tubers are eaten in India like potatoes. Roots are boiled with alum to make a yellow dye. Chopped nettles are fine food for young poultry. Many minor uses of various species might be named. The sting of the nettle is due to pointed hairs. Each hair contains a reservoir of liquid which is set free when the hard point of the hair is broken off in the flesh. If a nettle be grasped firmly with a sliding motion, these hairs are pressed down sideways and cannot enter the hand. A careless caress which merely touches the tips of the hairs is most to be regretted. Cold water only revives the pain. A dock leaf, rhubarb juice, or vinegar will relieve the pain. The sting of an East Indian nettle is described as like the blister of a hot iron, retaining its intensity for twenty-four hours and liable to return for eight days.
Collier's New Encyclopedia (1921)
a genus of plants (Urtica) belonging to the natural order Urticaceæ, and consisting chiefly of neglected weeds, alternate having opposite or leaves, and inconspicuous flowers, which are disposed in axillary racemes. The species are mostly herbaceous, and are usually cover covered with extremely fine, sharp, tubular hairs, placed on minute vesicles filled with an acrid and caustic fluid, which by pressure is injected into the wounds caused by the sharp-pointed hairs.
What Has Changed in the Last Century
The mechanics Aiton's described in 1910 — a brittle hair tip that snaps off in the skin and injects the fluid beneath it — is still how the sting is explained today. What has been filled in is the chemistry: the "acrid and caustic fluid" of Collier's 1921 entry was long assumed to be simply formic acid, but work from the late 1940s onward identified histamine, acetylcholine and serotonin as the agents behind the weal and the itch, and in 2020 researchers isolated novel neurotoxin peptides (dubbed gympietides) from the fiercest of the family, Australia's giant stinging trees — plausibly the sort of plant behind the tale of a sting like "the blister of a hot iron." Aiton's grouping of nettle with elm, hemp and hop has been redrawn: hemp and hop now sit in their own family, Cannabaceae, and elm in Ulmaceae, though all remain near relatives of Urtica within the order Rosales. The recommended dock leaf remains folk practice with no demonstrated chemical basis, while nettle fibre, once an old rope and cloth material, has returned as a niche textile crop.
Written for this edition, 2026.