A pearl is a lustrous concretion produced by certain bivalve molluscs (muscles and oysters) and valued as a gem. Pearls consist almost entirely of nacre, which is the substance forming the inner layers of the mollusc shells. Nacre, known as mother-of-pearl, is composed primarily of aragonite crystals. The pearl is an abnormalgrowth resulting from the invasion of the body of the mollusc by a minute parasitic worm (it was previously believed to be invasion by a grain of sand or similar which caused the pearl to be produced), which cannot escape and irritates the mollusc which retaliates by coating the irritant with layer upon layer of nacreous material. Both marine and freshwater molluscs produce pearls, but the most valuable varieties originate in the pearl oyster of the Persian Gulf. The most highly prized pearls are spherical. When a pearl that has been cut from the shell presents a hemispherical surface, it is sometimes called a bouton pearl. If a solid pearl has an irregular shape, having grown over a rough object, it is known as a baroque pearl. In the jewellerytrade, pearls are commonly known as pear, bell, or drop, according to the shape. Pearl coloration varies widely, the most prized shades being white, black, rose, and cream. River pearls are produced by freshwater mussels in various parts of the world. China is the principal trader in river pearls. Natural, spherical pearls have been cultured successfully since 1920. In this process a mother-of-pearl bead, from three-quarters to nine-tenths of the diameter of the desired product, is introduced into the
pearl oyster. Over a period of years the oyster deposits layers of nacre around the bead. Cultured pearls are not easily distinguished from genuine pearls except by an expert. The technique of producing spherical cultured pearls was developed in Japan, and the culturing of pearls is a major Japanese industry - a small bead of mother of pearl being inserted into the oyster which grows the pearl around the bead. Artificial pearls, in contrast to cultured pearls, are entirely man-made, largely of glass. Research Pearl
Adam's Pearmain is a late dessert apple, probably from Norfolk, which was a Victorian favourite because of its rich aromatic flavour and crisp texture. It was widely grown in the nineteenth century, when fruiterers ' always paid good prices because it was attractive for windows'. The pear shaped fruits are of a medium size and can be stored until March. The vigorous trees have a spreading habit and pretty blossom. Research Adam's Pearmain
The Anchovy-Pear (Grias cauliflora) is a tree of the natural order Myrtaceae, a native of Jamaica, growing to the height of fifteen meters, with large leaves and large white flowers, and bearing a fruit somewhat bigger than a hen's egg, which is pickled and eaten like the mango, which it strongly resembles in taste. Research Anchovy-Pear
Anona is a genus of plants, the type of the natural order Anonaceae. Anona squamdsa (sweet-sop) grows in the West Indian Islands, and yields an edible fruit having a thick, sweet, luscious pulp. Anona muricata, (sour-sop) is cultivated in the West and East Indies; it produces a large pear-shaped fruit, of a greenish colour, containing an agreeable slightly acidpulp. The genus produces other edible fruits, as the common custard-apple or bullock's heart, from Anona reticulata, and the cherimoyer of Peru, from Anona Cherimolia. Research Anona
The Apple Blossom Weevil (Anthonomus pomorum) is a species of Snout Beetle (Curculionidae) that lives chiefly on apple trees but also pear trees. The larvae eat the young buds damaging the petals so that the flowers do not open. Research Apple Blossom Weevil
The avocado-pear also known as the avocado, alligator pear or subaltern's butter (Persea gratissima) is an evergreen tree of the family Lauraceae. It has a brownish or puplish pear-shaped berry, weighing around one to two pounds, and filled with an oily, green pulp similar in texture to butter. It is a native tree of tropical America and the West Indies. Research Avocado
Abbreviations
Research Olpe
