• Webster's Revised Unabridged Dictionary
    • n Polymnia See Polyhymnia.
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Century Dictionary and Cyclopedia
    • n Polymnia See Polyhymnia.
    • n Polymnia A genus of composite plants of the tribe Helianthoideæ and subtribe Melampodieæ. It is characterized by ample leaves, either opposite or alternate above, and corymbose flower-heads with broad involucres, the outer row of bracts often large, leaf-like, and spreading, the ray-flowers in a single row or lacking altogether, and smooth, thick, and nearly cylindrical obovoid achenes, without awns. The 12 species are natives of America, and are found from Canada to Buenos Ayres. They are perennial herbs, shrubs, or trees, often viscid, with yellow flowers, and large angled, lobed, or entire leaves, generally appendaged at the petiole-base with a cup-like membrane, whence their name leafcup.
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In literature:

Pierides, tuneful nine (Calliope, Clio, Erato, Euterpe, Melpomene, Polymnia, Terpsichore, Thalia, Urania).
"Putnam's Word Book" by Louis A. Flemming
Polymnia was the name of their lyric muse.
"Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 2" by Various