Truffle
2 of the 7 encyclopedias on this shelf carry an entry for Truffle. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a genus of fungi of the order Tuberacei, division Ascomycetes; globose, or nearly so; of a fleshy substance, with a distinct skin, the whole substance pervaded by a network of serpentine veins, which are the hymenium, and bear the spore-cases in minute cavities. The species are not numerous; they are very generally diffused in temperate parts of the world; they are subterranean, often found at the depth of a foot or more in the soil, usually near the roots of trees, or rarely living on the surface. Some of them are among the most highly valued or esculent fungi. They are said stimulating aphrodisiacal to have a quality. The common truffle (T. æstivum) is of a black color, and has a warty surface. It is the principal species sold in the English markets. It varies in size from that of a large plum to that of a large potato. On account of its agreeable flavor, it is used in the preparation of many dishes. It is common in central and southern Europe, chiefly in loose soils, in woods and pastures, as in the chestnut woods of France and Italy.
Aiton's Encyclopedia (1910)
a genus of subterranean fungi, much esteemed as a table delicacy. There are about fifty species. They have the shape of a potato and are black or bluish outside with a white interior. They range in size from that of a Brazil nut to that of a large potato. They grow limy soil, usually in birch or oak forests. They never appear above ground. In France hogs are trained to root them out. In England dogs are trained to locate them and indicate their presence by scratching. In both cases the finder is rewarded, the sow by an acorn, the dog by some other dainty. The truffles of France are the most celebrated. See Fungus; Mushroom