The Collaborative International Dictionary of English v.0.48:

Malcolm stock \Malcolm stock\ n.
   Any of various ornamental flowering plants of the genus
   Malcolmia.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

Malcolm stock
    n 1: any of various ornamental flowering plants of the genus
         Malcolmia [syn: Malcolm stock, stock]