actually hard-shelled seeds which are produced in groups of between 12 and 30 within a large, hard, thick-walled woody fruit or pod. The sweet-tasting nut meat is consumed in the fresh state and Brazil nut oil may be extracted for use as a lubricant.

Cashew nut The cashew (Anacardium occidentale) originated in Brazil but is now cultivated extensively in all tropical areas, notably in India and East Africa. The cashew fruit, which contains the seed or 'nut,' hangs at the end of what is referred to as the cashew 'apple'—the edible swollen fruit stem or pedicel. The fruit itself is kidney-shaped, about the size of a large bean, and has a two-layered shell. The outer layer of this shell contains a caustic oil that must be burned off before the nut is touched. The nuts are then roasted again or boiled to remove other toxic substances and the second shell is removed. The nuts may also be used as a source of oil.

Chestnut The sweet or Spanish chestnut (Castanea sativa) is a native tree of southern Europe, believed to have been introduced into Britain by the Romans. The fruit consists of two to four compartmentalized seeds or burrs, covered with numerous needle-sharp branched spines and containing the seeds or 'nuts,' which are covered with a tough outer coat. The flesh of the nut is hard and inedible and is cooked, often by roasting or boiling, before being eaten. The cooking process changes the texture so that the chestnut becomes much softer than other nuts and more like a vegetable, largely as a result of its high carbohydrate content (see below).

Coconut The coconut (Cocos nucifera) grows on the coconut palm, which is common in tropical areas throughout the world. The native origin of the palm is uncertain, as the nuts were easily dispersed between both islands and continents by ocean currents and by early explorers. The fruits are borne on the tree in clusters of about 15 to 20 and are enclosed in a thick outer husk and covered in a mass of fibers (the mesocarp and exocarp), which is normally removed when the coconut is harvested. The familiar hard shell of the coconut is the endocarp, or inner layer, of the mature ovary of the fruit, and within the shell is the actual seed, covered with a thin brown seed coat. The white coconut 'meat,' which can be eaten either fresh or desiccated, is actually part of the endosperm (storage tissue) of the seed. Coconut 'milk,' which is found in the unripe nut and is drunk or used in cooking, is the liquid form of the endosperm, which solidifies as the fruit ripens. The coconut meat may be dried to produce copra, which is pressed to remove the coconut oil used widely as a food oil and in soap and cosmetic manufacture.

Hazelnut (cobnut; filbert) The most widely grown hazelnut (Corylus avellana) is a native of Europe, although about 10 different species of Corylus grow throughout Europe, North America, and Asia. There is evidence that these nuts were cultivated in Ancient Greece and collected by Mesolithic peoples. The shell of the hazelnut is the matured ovary wall of the flower and the edible nut meat within this is the matured embryo.

Macadamia nut The macadamia nut (Macadamia integrifolia), smooth-shelled; M. tetraphylla, rough-shelled) is native to eastern tropical Australia but was subsequently introduced to Hawaii, which is now the leading producer of these nuts, and also to parts of Africa and South America. It is the smooth-shelled variety that has been developed commercially. The edible kernel of the nut is the seed, consisting mostly of the cotyledons of the embryo. It is enclosed in a hard, thick, brown shell, which is itself encased in a fibrous husk that splits open when the husk dries. This occurs after the fruit falls, or when it is removed from the tree at maturity. After harvesting, the nuts are dried (to a moisture level of 1.5%), roasted (traditionally in coconut oil, or dry-roasted), and salted.

Peanut The peanut (Arachis hypogaea), sometimes referred to as the ground nut or monkey nut, originated in South America. Although referred to as a nut, it is in fact part of the legume family. The plant was introduced to Africa by early European explorers and to North America by the slave trade; it was also introduced to India and China. The name 'ground nut' derives from the fact that the flower withers after pollination to leave a stalk-like part of the plant, which pushes under the soil and carries the fertilized ovules in its tip. Underground, the tip continues to develop into the characteristic pod of the peanut, containing the seeds, or 'nuts.' The shape and size of the pod, and the number and color of the seeds, are variable, depending on the peanut cultivar. On a worldwide basis, two-thirds of the peanut crop is crushed for oil (arachis oil) and peanut products are used widely in both food processing, with peanut butter as an important product, and for animal feed. The peanut itself may be eaten fresh or roasted and salted.

Pecan The pecan (Carya illinoinensis) is a member of the walnut family, and the tree is classified botanically as a hickory. The tree is a native of North America, grown in the southern central states. After harvesting, the nuts are air-dried to remove 10-20% of their moisture. The nut is similar to the walnut, but with a more mild and sweet flavor. The pecan nut kernel is eaten fresh and in the US it is used widely in confectionery and baked goods.

Pine nuts Pine nuts or kernels are small edible seeds which are extracted from the cones of various species of pine. The most commonly eaten variety is that from the European stone pine (Pinus pinea), which is native to northern Mediterranean regions. The small, oil-rich seeds are encased in a hard shell. The seeds are sometimes referred to as pignolia nuts, whereas the seeds of the pinyon pines (Pinus edulis and Pinus monophylla), which grow in the southwestern US and in northern Mexico, are known as pinon nuts.

Pistachio nut The pistachio nut is the seed of the pistachio tree (Pistacia vera). It is a native of central Asia, Pakistan, and India, where it was cultivated 3000 years ago, and it has also been cultivated for many years in Mediterranean regions and more recently in California. The pistachio fruit is similar to a peach; the outer 'husk' (the exocarp and meso-carp of the fruit) encloses a hard but thin off-white shell (the endocarp). This splits open just before the nut matures to reveal the edible embryo, which consists mainly of two green cotyledons covered in a thin seed coat. The green nut kernels are highly prized and are eaten roasted and salted as well as in various Middle Eastern dishes.

Walnut The walnut (Juglans spp.) is the common name given to about 20 species of trees in this family. The most important species is Juglans regia—the English or Persian walnut—which is believed to have originated in Ancient Persia, later taken to Greece, and eventually distributed throughout the Roman empire. There are records of its growth in England in the sixteenth century. It was taken to America and called the English walnut to distinguish it from the native American black walnut (Juglans nigrans) and the butternut (Juglans cinerea), both of which have much thicker, less brittle shells. The walnut fruit has an outer leathery husk and an inner furrowed stone, which is the shell of the nut, within which is the edible seed.

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