Their leaves are attached at the nodes and consist of two parts. The sheath clasps the stem (also known as the culm) sometimes all the way up to or beyond the next node. The blade is the upper part of the leaf that is free from the stem. The fact that the top edges of the sheath may overlap each other around the stem but are not joined to each other is a defining characteristic of grasses. At the point where the blade joins the sheath, there may be a flap of tissue called a ligule. This structure keeps dirt and parasites from getting into the space between the sheath and the stem.
The tiny grass flower, called a spikelet, is actually a composite of one or more tiny flowers and is the most characteristic structure among grasses. It is generally composed of two bracts called glumes, with one to many tiny flowers called florets attached above them. Each floret consists of a bract called a lemma that generally wraps around a smaller and generally very thin bract called a palea. These two encase the nearly microscopic rudimentary petals called lodicules, the stamens (usually one to three), and the ovary, which can have two or three feathery stigmas at its apex.
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