lawsonia inermis

from The Collaborative International Dictionary of English v.0.48

Henna \Hen"na\, n. [Ar. hinn[=a] alcanna ({Lawsonia inermis}
   syn. {Lawsonia alba}). Cf. {Alcanna}, {Alkanet}, {Orchanet}.]
   [1913 Webster]
   1. (Bot.) A thorny tree or shrub of the genus {Lawsonia}
      ({Lawsonia alba}). The fragrant white blossoms are used by
      the Buddhists in religious ceremonies. The powdered leaves
      furnish a red coloring matter used in the East to stain
      the nails and fingers, the manes of horses, etc.
      [1913 Webster]

   2. (Com.) The leaves of the henna plant, or a preparation or
      dyestuff made from them.
      [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Lawsonia \Law*so"ni*a\, n. (Bot.)
   An Asiatic and North African shrub ({Lawsonia inermis}), with
   smooth oval leaves, and fragrant white flowers. {Henna} is
   prepared from the leaves and twigs. In England the shrub is
   called {Egyptian privet}, and in the West Indies, {Jamaica
   mignonette}.
   [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Alcanna \Al*can"na\, n. [Sp. alcana, alhe?a, fr. Ar.
   al-hinn[=a]. See {Henna}, and cf. {Alkanet}.] (Bot.)
   An oriental shrub ({Lawsonia inermis}) from which henna is
   obtained.
   [1913 Webster]