Avocado, also called alligator pear, fruit of Persea americana of the family Lauraceae, a tree native to the Western Hemisphere from Mexico south to the Andean regions. Avocado fruits have greenish or yellowish flesh with a buttery consistency and a rich, nutty flavour. They are often eaten in salads, and in many parts of the world they are eaten as a dessert. Mashed avocado is the principal ingredient of guacamole, a characteristic sauce in Mexican cuisine. Avocados provide thiamin, riboflavin, and vitamin A, and in some varieties the flesh contains as much as 25 percent unsaturated oil.Avocado trees can be tall or spreading, and they have elliptic to egg-shaped leaves that are 10-30 cm (4-12 inches) in length. The small greenish flowers are borne in dense inflorescences and lack true petals. The flowers have nine stamens, arranged in three series, and a one-celled ovary. Interestingly, there are two types of avocado flowers, A and B, depending on the cultivar. These flowers are dichogamous (male and female parts mature separately), and each flower opens only twice. Type A flowers are functionally female in the morning, close at midday, and then reopen as functionally male in the afternoon of the following day. Type B flowers are functionally female in the afternoon, close in the evening, and then reopen the following morning as functionally male. When the two flower types are grown together, this temporal overlap of mature male and female parts encourages cross-pollination and, thus, greater fruit production.The fruit is exceedingly variable in size, no larger than a hen's egg in certain Mexican races and sometimes weighing 1-2 kg (2-4 pounds) in other races. The form varies from round to pear-shaped with a long, slender neck, and the colour ranges from green to dark purple. Botanically, the fruit is a berry and features a single large round seed with two cotyledons. The fruit's outer skin is sometimes no thicker than that of an apple and sometimes is coarse and woody in texture.Avocados were first domesticated in tropical America, where they were cultivated as individual seedling trees before the Spanish conquest. The plants did not receive serious horticultural attention until about 1900, when horticulturists found that production of grafted trees was simple and allowed perpetuation of superior seedlings and the establishment of orchards. Flourishing avocado industries have since developed around the world in suitable climates. Mexico, Chile, the Dominican Republic, Indonesia, and Colombia were the top producers worldwide in 2011. The fruits are also grown commercially in Florida, California, Hawaii, South Africa, Brazil, and Australia, as well as on some Pacific islands and in several Mediterranean countries, including Israel.Horticulturally, avocados are divided into the Mexican (Persea americana variety drymifolia), West Indian (P. americana variety americana), and Guatemalan (P. americana variety guatemalensis) races, with more than 1,000 cultivars between them. The Mexican race is native to Mexico and is characterized by the aniselike odour of the leaves and by small (weighing 90-240 grams [3-8 ounces]), thin-skinned fruits of rich flavour and excellent quality. Mexican avocados are the hardiest, growing in regions too cold for other types. The Guatemalan, native to the highlands of Central America, is slightly less frost-resistant than the Mexican and produces fruits of medium to large size (240-1,000 grams), characterized by thick woody skins and a ripening season different from that of the others. Cultivation of the West Indian, the most tropical in character, is limited in the United States to southern Florida. Hass avocado, the most popular cultivar in the United States, is a Mexican-Guatemalan hybrid.