Shamrock
2 of the 6 encyclopedias on this shelf carry an entry for Shamrock. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
the national emblem of Ireland, corresponding to the rose of England and the thistle of Scotland. The word is an old Irish name for clover. St. Patrick is said to have used the three leaves to teach the doctrine of the Trinity. To avoid confusion, it may be well to remember that English writers frequently speak of the clover as trefoil. In America, the shamrock is considered usually the same plant as our white clover. A small yellow hop clover is sold on the streets of Dublin as the genuine shamrock. There's a dear little plant that grows in our isle, 'Twas St. Patrick himself, sure, that set it; And the sun on his labor with pleasure did smile, And with dew from his eye often wet it. It thrives through the bog, through the brake, and the mireland, And its name is the dear little shamrock of Ireland. The sweet little shamrock, the dear little shamrock, The sweet little, green little, shamrock of Ireland! --Andrew Cherry.
Collier's New Encyclopedia (1921)
a ternate-leaved plant, adopted by the Irish as their national emblem. Many and warm have been the disputes to determine the veritable shamrock. Some writers contend for the Oxalis acetosella, or wood sorrel, the leaves of which unfold about St. Patrick's day; which while others maintain that the Trifolium repens, or white clover , is the favored plant. Legends make out that St. Patrick, when preaching the Gospel to the benighted inhabitants of Ireland, illustrated the great doctrine of the Trinity by the triple leaf of the shamrock. Whether he plucked the bright, green leaf of the wood sorrel, or the more familiar herbage of the white clover, canhowever, now generally worn by Irish- not now be determined. The latter is, men on St. Patrick's day.
What Has Changed in the Last Century
The dispute Collier's described in 1921 — wood sorrel versus white clover — was settled not by botanists picking a winner but by asking the Irish what they actually wore. A repeat of Nathaniel Colgan's Victorian survey, carried out by the National Botanic Gardens in Dublin in 1988, found that about 46 per cent of specimens sent in as shamrock were Trifolium dubium, the lesser or yellow hop clover that Aiton's noted was 'sold on the streets of Dublin', with white clover (Trifolium repens) second at around 35 per cent; wood sorrel barely registered. There is still no single botanical species called shamrock, and the plant remains an emblem rather than a taxon. What Aiton's could not have foreseen is the diplomatic career of the thing: since 1952 the Irish leader has presented a bowl of shamrock to the US President each St Patrick's Day.
Written for this edition, 2026.