known colloquially as the "core". From the upper rim of the receptacle are given off the five sepals, the five petals, and the very numerous stamens. Pears and apples cannot always be distinguished by the form of the fruit; some pears look very much like some apples, e.g. the nashi pear. One major difference is that the flesh of pear fruit contains stone cells. History Pear cultivation in cool, temperate climates extends to the remotest antiquity, and evidence exists of its use as a food since prehistoric times. Many traces have been found in prehistoric pile dwellings around Lake Zurich. Pears were cultivated in China as early as 2000 BC. An article on Pear tree cultivation in Spain is brought down in Ibn al-'Awwam's 12th-century agricultural work, Book on Agriculture. The word pear, or its equivalent, occurs in all the Celtic languages, while in Slavic and other dialects, differing appellations, still referring to the same thing, are found—a diversity and multiplicity of nomenclature, which led Alphonse Pyramus de Candolle to infer a very ancient cultivation of the tree from the shores of the Caspian to those of the Atlantic. The pear was also cultivated by the Romans, who ate the fruits raw or cooked, just like apples. Pliny's Natural History recommended stewing them with honey and noted three dozen varieties. The Roman cookbook De re coquinaria has a recipe for a spiced, stewed-pear patina, or soufflé. Romans also introduced the fruit to Britain. A certain race of pears, with white down on the undersurface of their leaves, is supposed to have originated from P. nivalis, and their fruit is chiefly used in France in the manufacture of perry (see also cider). Other small-fruited pears, distinguished by their early ripening and apple-like fruit, may be referred to as P. cordata, a species found wild in western France and southwestern England. The genus is thought to have originated in present-day Western China in the foothills of the Tian Shan, a mountain range of Central Asia, and to have spread to the north and south along mountain chains, evolving into a diverse group of over 20 widely recognized primary species. The enormous number of varieties of the cultivated European pear (Pyrus communis subsp. communis), are without doubt derived from one or two wild subspecies (P. c. subsp. pyraster and P. c. subsp. caucasica), widely distributed throughout Europe, and sometimes forming part of the