There is variation even in this type of rhizome. unifolium) each bulb produces one or more rhizomes that in turn produce a terminal renewal or increase bulb. validum) bulbs form atop a thick, iris-like rhizome that produces new bulbs in succeeding years. In addition several types of rhizomes are formed in Allium. Often the meristem will branch, resulting in two or more bulbs being formed from a single parent bulb (increase bulbs). The leaf bases are replaced annually as the meristem forms a new (renewal) bulb. The Allium bulb consists of a series of leaf bases, some with blades, others without, surrounding an apical meristem. It is anticipated, therefore, that it can be used successfully only with considerable understanding of the natural units involved, their distribution, and comparison with descriptions and accurately named specimens. Many of these are subject to sometimes rather wide variation. The characters used in the construction of the following key are the best that have been discovered for this purpose. Resolution of the problematic subgeneric and sectional relationships among Old and New World species will require much more extensive molecular and phylogenetic analysis of the genus. ![]() These latter species have been placed in subg. Hanelt (1992) placed the Old World x = 7 species also in that subgenus, which includes all but three of the North American species (A. Amerallium, encompassing all of the x = 7 North American members of the genus. Attempts to treat New World species similarly have gained less acceptance. Thorne 1992).Old World species of Allium are generally placed in subgenera and sections. As with many other genera in the Liliaceae sensu lato, Allium has been segregated into a separate family, Alliaceae, by most recent authors (R. Seeds black, obovoid, finely cellular-reticulate, cells smooth or minutely roughened, with 1-8 papillae, without caruncle except in A. lacunosum style 1 stigma capitate to ± 3-lobed pedicel erect or spreading (lax in A. nigrum), crest processes 3 or 6, smooth except in A. ![]() hoffmanii papillose to ciliate proximally) anthers and pollen variously colored ovary superior, 3-lobed, sometimes crested with processes, 3-locular, usually 2 ovules per locule (6-8 in A. victorialis appendaged), linear, generally glabrous (A. triquetrum) tepals 6, in 2 similar whorls, ± distinct, petallike, usually becoming becoming dry and persisting stamens 6, epipetalous filaments in all but 1 native species broad at base, fused into ring (some introduced species and A. schoenoprasum), sometimes replaced totally or partially by bulbils, subtended by spathe bracts bracts conspicuous, ± fused, usually 3+-veined, equaling pedicel except in some introduced species, membranous. Inflorescences umbellate, flowering centripetally (centrifugally in A. ![]() Scape usually persistent, terete or flattened. lacunosum), straight or ± falcate (coiled or circinate in A. Leaves generally withering from tip by anthesis, usually persistent, 1-12, basal blade usually linear, terete, channeled, or flat (carinate in A. Bulbs solitary or clustered, dividing at base, or on rhizomes, reforming annually outer coats generally brown or gray, smooth, fibrous, or with cellular reticulation (generally important in identification) inner coats membranous. Herbs, perennial, scapose, from tunicate bulbs, with onion odor and taste.
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