The var. graminifolia, mostly diploid, with the heads of var. aspera and the pubescence of var. latifolia, occurs mainly on the coastal plain from N.C. to Fla. and Tex. (var. microcephala)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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