The Collaborative International Dictionary of English v.0.48:

Chara \Cha"ra\, n. [NL., of uncertain origin.] (Bot.)
   A genus of flowerless plants, having articulated stems and
   whorled branches. They flourish in wet places.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Chara
    n 1: green algae common in freshwater lakes of limestone
         districts [syn: Chara, genus Chara]