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Poaceae

Eriochloa Kunth

Kingdom: Plantae Rank: Genus Parent: Poaceae Status: Valid

Common Names:

  • CUP GRASS - English, United States of America

Morphological Description

Diagnosis: Annuals or perennials; ligule of hairs to 1–2 mm long; panicle slender, of erect, appressed, spikelike racemes along a main axis; spikelets each with a small (< 0.5 mm long) cup-like collar or ring (called the callus) just under the base, solitary or paired, 2-flowered, the lower staminate or neuter, the upper perfect; disarticulation at base of spikelets; lower glume absent (see note in synopsis below); upper glume and lemma of sterile floret similar.

Other

Notes: A C₄ genus of 20–30 species of tropical and warm areas of the world (Shaw & Smeins 1981; Shaw et al. 2003). More than two-thirds of the taxa are found in the American southwest and in the central Andes (Shaw & Smeins 1981). Some species are important pasture grasses while others are considered significant weeds (Watson & Dallwitz 1992). The small cup-like structure below the spikelets, known as the callus, is quite unique and distinguishes the genus from all other members of its tribe (Shaw & Webster 1987). Its anatomical derivation has been studied in detail (Shaw & Smeins 1979, 1983; Thompson et al. 1990) with conflicting conclusions. Shaw and Smeins (1983) concluded that it represents swollen or expanded internode tissue fused with the much-reduced lower glume. Thompson et al. (1990), however, found that it lacks vascular tissue, is formed entirely of parenchymatous tissue, and that glume tissue is not involved. They concluded that it is “formed by a proliferation of the ground tissue at the spikelet base.” Davidse (1987a) suggested a possible function—the cup-shaped structure might contain lipids and function as an elaiosome to attract ants that would act as dispersal agents for the seeds. (Greek: erion, wool, and chloa, grass, in reference to the densely hairy pedicels and spikelets of the type species—Shaw & Webster 1981) (subfamily Panicoideae, tribe Paniceae)