From The Collaborative International Dictionary of English v.0.48 :
Ricinus \Ric"i*nus\, n. [L., the castor-oil plant.] (Bot.) A genus of plants of the Spurge family, containing but one species ({Ricinus communis), the castor-oil plant. The fruit is three-celled, and contains three large seeds from which castor oil is expressed. See Palma Christi. [1913 Webster]From WordNet (r) 3.0 (2006) :
Ricinus n 1: a genus of herb having only one known species: castor-oil plant [syn: Ricinus, genus Ricinus]