Source : Webster's Revised Unabridged Dictionary (1913)

Parella \Pa*rel"la\, Parelle \Pa`relle\, n. [Cf. F. parelle.]
   (Bot.)
   (a) A name for two kinds of dock ({Rumex Patientia} and {R.
       Hydrolapathum}).
   (b) A kind of lichen ({Lecanora parella}) once used in dyeing
       and in the preparation of litmus.