idioblast

from The Collaborative International Dictionary of English v.0.48

Idioblast \Id"i*o*blast\ ([i^]d"[i^]*[-o]*bl[a^]st), n. [Ideo- +
   -blast.] (Bot.)
   An individual cell, differing greatly from its neighbours in
   regard to size, structure, or contents.
   [1913 Webster]