Plum
2 of the 7 encyclopedias on this shelf carry an entry for Plum. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a fruit-bearing shrub akin to the peach, almond, and cherry. It is pretty difficult to classify plums. Of native plums we have the common wild plum of the North, the Chickasaw plum of the South, the sand plum of the plains, the beach plum of the Atlantic coast, and the Pacific plum. Of plums introduced we have the apricot plum from China, Japanese plums, cherry plums, and domestic plums from Europe. Prunes are sweet plums that may be dried on the pit without fermentation or souring. Damsons and green gages are well known plum types. As in the case of apples, plum trees are propagated by planting seeds, grafting, and seedlings. Some nurserymen graft plum twigs on peach seedlings. California is our chief plum-producing state. Freedom from insect plagues, with soil and climate unsurpassed, has brought the state forward to a prune production of 337,000,000 pounds in 1900, not including canned plums and enormous shipments of crated green fruit. Plum blossoms appear in early spring before the leaves. They rival apple blossoms in fragrance. On account of their hardiness, plum trees are raised probably in more dooryards than any other fruit tree. The real way to enjoy plums, however, is to find wild plums in the woods and eat them before going home. See Prunes
Collier's New Encyclopedia (1921)
the fruit of sub-species of P. the common plum, a tree itself. It is a communis or that and Asia Minor, native of the Caucasus it was introduced into Europe at a very early period. It has run into varieties. more than 300