page_title: Monocotyledon
section_title: Vascular system
hierarchical_section_title: Monocotyledon / Description / Vascular system
caption_attribution_description: English: Royal Palm Trunk
context_page_description: Monocotyledons, commonly referred to as monocots, are grass and grass-like flowering plants, the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of the major groups into which the flowering plants have traditionally been divided, the rest of the flowering plants having two cotyledons and therefore classified as dicotyledons, or dicots.
  Monocotyledons have almost always been recognized as a group, but with various taxonomic ranks and under several different names. The APG III system of 2009 recognises a clade called "monocots" but does not assign it to a taxonomic rank.
  The monocotyledons include about 60,000 species. The largest family in this group by number of species are the orchids, with more than 20,000 species. About half as many species belong to the true grasses, which are economically the most important family of monocotyledons. Often mistaken for grasses, sedges are also monocots.
  In agriculture the majority of the biomass produced comes from monocotyledons. These include not only major grains, but also forage grasses, sugar cane, and the bamboos.
context_section_description: Monocots have a distinctive arrangement of vascular tissue known as an atactostele in which the vascular tissue is scattered rather than arranged in concentric rings. Collenchyma is absent in monocot stems, roots and leaves. Many monocots are herbaceous and do not have the ability to increase the width of a stem (secondary growth) via the same kind of vascular cambium found in non-monocot woody plants. However, some monocots do have secondary growth; because this does not arise from a single vascular cambium producing xylem inwards and phloem outwards, it is termed "anomalous secondary growth".  Examples of large monocots which either exhibit secondary growth, or can reach large sizes without it, are palms (Arecaceae), screwpines (Pandanaceae), bananas (Musaceae), Yucca, Aloe, Dracaena, and Cordyline.
caption: Roystonea regia palm (Arecales) stems showing anomalous secondary growth in monocots, with characteristic fibrous roots
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