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In common parlance, sedges and rushes often become just “some kind of grass.” Yet sedges, grasses, and rushes, which make up almost all of the grasslike plants in temperate ecosystems, comprise three separate families: the Cyperaceae (the sedge family, approximately 5,000 species worldwide), Poaceae (the grass family, also known by the name Gramineae, approximately 10,000 species), and Juncaceae (the rush family, approximately 400 species). We need only look at a few common names to see the way in which these families are intermixed in the common view: spike-rushes (Eleocharis spp.), bulrushes (Scirpus spp., Schoenoplectus spp.), nut-rushes (Scleria spp.), and even some common “wiregrasses” (e.g., Carex lasiocarpa and C. oligosperma ) are members of the Cyperaceae, not true rushes or grasses. These families, while closely related to one another, do not interbreed and are ecologically and morphologically distinct from one another. Moreover , with a little study they are easy to distinguish from one another. Most of the major genera are easy to tell apart as well. By the end of this chapter you should be able to distinguish the Poaceae, Cyperaceae, and Juncaceae and recognize the genus Carex in the Weld. Once you can do this, you will be well on your way to learning sedges. DISTINGUISHING SEDGES FROM GRASSES AND RUSHES Distinguishing the Cyperaceae, Juncaceae, and Poaceae based on inXorescence characters is straightforward with a hand lens and fruiting or Xowering material. The inXorescence of the rushes (Juncaceae) is the simplest of the three families, with Xowers typically bisexual, subtended by 6 small, green or brown, petal-like structures (tepals). The rush Xower thus resembles a small lily, and rushes were in the past hypothesized to be closely related to the lilies, with Xowers reduced under selective pressure for wind pollination. Considerable anatomical and molecular data, however, demonstrate that in 6 What Is a Sedge? fact the Juncaceae are sister to the Cyperaceae, and neither is very closely related to the lilies. The sedge (Cyperaceae) inXorescence comprises unisexual or bisexual Xowers that are each subtended by a single scale. In Carex, discussed in greater detail below, each female Xower is additionally enclosed in a highly modiWed bract called a perigynium or utricle. Grasses (Poaceae) are the most complex of the three families in inXorescence structure, producing bisexual Xowers surrounded by numerous specialized scales. Each individual Xower, or Xoret, is enclosed in a two-scale sandwich, a lemma on the outside and a palea on the inside. The Xorets are borne in inXorescence units called spikelets, which are themselves surrounded by specialized scales called glumes. The families are also easily recognized by the structure of the fruits. As with their inXorescence structure, rushes (Juncaceae) are the most distinctive of the three families in fruit type, producing a capsule that contains many small seeds in the genus Juncus (the rushes), three seeds per capsule in Luzula (the wood rushes). The morphology of these seeds is key to identifying the different species of Juncus, making the collection of mature fruits as important in rush taxonomy as it is in identifying sedges. The sedges (Cyperaceae) produce small achenes that are highly variable in morphology. They range from lens-shaped (lenticular) to three-sided or round in cross-section. They may be black, chestnut, or green. Their surfaces range from entirely smooth to highly rugose, roughened, or striated, with prominent bristles characteristic of species in many genera. This diversity is restricted within the genus Carex, in which achenes are enclosed within the perigynium and typically smooth, almost never ornamented. Achene characteristics are nonetheless important in the identiWcation of many species in the genus. The grasses (Poaceae) produce a specialized achene called a karyopsis, which differs in having the seed coat completely fused to the fruit wall. Yet often only vegetative structures are available, so it is fortunate that we can distinguish the families by vegetative characters alone. Many people are Wrst introduced to graminoid taxonomy through the rhyme “sedges have edges.” In fact, the shoots of many sedges are triangular in cross-section. The genus Carex in particular has many species with prominently triangular culms and vegetative shoots. Many of the bulrushes (species in the genus Schoenoplectus and some of its allies) and spike-rushes (Eleocharis), however, have culms that are more often round in cross-section. Culm cross-section also provides useful characters for distinguishing the families: while the culms of grasses are typically hollow, with prominent, jointlike nodes, the culms of sedges and rushes are more often solid between...

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