cau·dex /ˈkɔˌdɛks/
  Cau·dex n.; pl. L. Caudices E. Caudexes   Bot. The stem of a tree., esp. a stem without a branch, as of a palm or a tree fern; also, the perennial rootstock of an herbaceous plant.
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  caudex
       n 1: persistent thickened stem of a herbaceous perennial plant
            [syn: stock]
       2: woody stem of palms and tree ferns
       [also: caudices (pl)]