1.2-Genus Allium + Overview In the APG III classification system, Allium is placed in the familyAmaryllidaceae, subfamily Allioideae (formerly the family Alliaceae). In some of the older classification systems, Allium was placed in Liliaceae. Molecular phylogenetic studies have shown this circumscription of Liliaceae is not monophyletic. Allium is one of about fifty-seven genera of flowering plants with more than 500 species. It is by far the largest genus in the Amaryllidaceae, and also in the Alliaceae in classificationsystems in which that family is recognized as separate. The onion genus Allium comprises monocotyledonousflowering plants and includes the onion, garlic, chives, scallion, shallot, and the leek as well as hundreds of wild species. The generic nameAllium is the Latin word for garlic; Linnaeus used allium specifically.Some sources may refer to Greek αλεω (to avoid) by reason of the smell of garlic. The almost universal eating and cooking of parts of the plants owes to the large variety of flavours and textures of the species. After cultivation from time immemorial about a dozen species are economically important as crops, or garden vegetables, and an increasing number of species are important as ornamental plants. The allocation of a plant to the Allium genus is taxonomically difficult and species boundaries are unclear. Most authorities accept about 750 species. Estimates of the number of species have been as low as 260, and as high as 979. The type species for the genus is Allium sativum. Allium species occur in temperate climates of the northern hemisphere, except for a few species occurring in Chile (such as Allium juncifolium), Brazil (Allium sellovianum), and tropical Africa (Allium spathaceum). They vary in height between 5 cm and 150 cm. The flowersform an umbel at the top of a leafless stalk. The bulbsvary in size between species, from small (around 2-3 mm in diameter) to rather large (8-10 cm). Some species (such as Welsh onion A. fistulosum) develop thickened leaf-bases rather than forming bulbs as such. Plants of the Allium genus produce chemical compounds (mostly derived from cysteine sulfoxides) that give them a characteristic (alliaceous) onion or garlic taste and odor. Many are used as food plants, though not all members of the genus are equally flavorous. In most cases, both bulb and leaves are edible and the taste may be strong or weak, depending on the species and on ground sulfur (usually as sulfate) content. In the rare occurrence of sulfur-free growth conditions, all Allium species lose their usual pungency altogether. + Genera Tribe Allieae has one genus and over 500 species: Genus Allium L. (includes Milula Prain) The genus contains hundreds of distinct species; many have been harvested through human history, but only about a dozen are still economically important today as crops or garden vegetables. Many others are cultivated as ornamental plants.
2- Characteristics of the Genus Allium
2.1-Description Allium species are herbaceous perennials with flowers produced on scapes. They grow from solitary or clustered tunicate bulbs and many have an onion odor and taste. Plants are perennialized by bulbs that reform annually from the base of the old bulb, or are produced on the ends of rhizomes or, in a few species, at the ends of stolons. A small number of species have tuberous roots. The bulbs' outer coats are commonly brown or grey, with a smooth texture, and are fibrous, or with cellular reticulation. The inner coats of the bulbs are membranous. Many alliums have basal leaves that commonly wither away from the tips downward before or while the plants flower, but some species have persistent foliage. Plants produce from one to 12 leaves, most species having linear, channeled or flat leaf blades. The leaf blades are straight or variously coiled, but some species have broad leaves, including A. victorialis and A. tricoccum. The leaves are sessile, and very rarely narrowed into a petiole. The flowers are erect or in some species pendent, having six petal-like tepals produced in two whorls. The flowers have one style and six epipetalous stamens; the anthers and pollen can vary in color depending on the species. The ovaries are superior, and three-lobed with three locules. The fruits are capsules that open longitudinally along the capsule wall between the partitions of the locule. The seeds are black, and have a rounded shape. The terete or flattened flowering scapes are normally persistent. The inflorescences are umbels, in which the outside flowers bloom first and flowering progresses to the inside. Some species produce bulbils within the umbels, and in some species, such as Allium paradoxum, the bulbils replace some or all the flowers. The umbels are subtended by noticeable spathe bracts, which are commonly fused and normally have around three veins. Some bulbous alliums increase by forming little bulbs or "offsets" around the old one, as well as by seed. Several species can form many bulbils in the flowerhead; in the so-called "tree onion" or Egyptian onion (Allium × proliferum) the bulbils are few, but large enough to be pickled. Many of the species of Allium have been used as food items throughout their ranges. There are several poisonous species that are somewhat similar in appearance (e.g. in North America, death camas, Toxicoscordion venenosum), but none of these has the distinctive scent of onions or garlic.
3.2- The most important species Many Allium species have been harvested through human history, but only about a dozen are still economically important today as crops or garden vegetables. The most important species include: 1- Onions (Allium cepa) 2- French shallots (Allium oschaninii) 3- Leeks (Allium ampeloprasum) 4- Scallions (various Allium species) 5- Garlic (Allium sativum) 6- Chives (Allium schoenoprasum) See also:List of Allium species Source: Allium- From Wikipedia, the free encyclopedia