The 1923 volume Aconitum is not a book in the ordinary sense. It is a photographic reference archive — a filing cabinet's worth of index cards, each pasted with a photograph and annotated in the crisp, clerical hand of the horticultural printing trade. Every card carries the same header:

"Proofs of engravings made from this photograph are pasted below."

The photographs catalogued dozens of varieties. One card reads:

"Variety Za pellices... Origin... Date 9-15-58... Remarks..."

The forgotten fact is not in the words. It is in the sheer existence of the archive.

Who was McFarland? J. Horace McFarland (1859–1948) ran Mount Pleasant Press in Harrisburg, Pennsylvania — the printer that produced most of America's finest seed catalogs, rose books, and nursery brochures for half a century. He was the founding president of the American Civic Association, one of the loudest lobbying voices behind the creation of the National Park Service in 1916, and the man who essentially invented full-color horticultural printing in the United States. He built a photograph library of some 40,000 plant images so that engravers and lithographers could pull accurate reference material for any catalog on demand. It was, in effect, Google Images for gardeners — assembled a century before the internet.

The forgotten claim, hidden in the filing: That a printer needed a filing cabinet of Aconitum varieties in 1923 tells us that Aconitum — better known as monkshood, wolfsbane, or the "queen of poisons" — was a mainstream ornamental. It was in cottage borders, church gardens, and mail-order catalogs. McFarland's archive documented named cultivars ('Sparks Variety', 'Bicolor', 'Bressingham Spire') the way we now document coneflowers.

Modern reality: Every part of Aconitum contains aconitine, one of the most potent plant neurotoxins known. As little as 2 milligrams — an amount easily absorbed through unbroken skin — can kill an adult. In 2010, a British gardener named Nathan Greenaway died after brushing against monkshood while working at an estate. In 2014, a British landscape gardener was murdered with Aconitum curry. Modern extension services now warn against growing it near vegetable beds, or at all around children.

• Victorian herbalists prescribed it for fevers and neuralgia at homeopathic dilutions.
• Nazi scientists reportedly tested it as a bullet poison.
• It is the plant Snape asks Harry Potter to identify on his first day of Potions.

McFarland's card catalog is a snapshot of a moment when Americans planted, photographed, and traded named varieties of a plant that could kill their toddlers by touch — and no one thought this was remarkable enough to note in the "Remarks" line.