indehiscent

from WordNet (r) 3.0 (2006)

indehiscent
    adj 1: (of e.g. fruits) not opening spontaneously at maturity to
           release seeds [ant: {dehiscent}]

from The Collaborative International Dictionary of English v.0.48

Indehiscent \In`de*his"cent\, a. [Pref. in- not + dehiscent: cf.
   F. ind['e]hiscent.] (Bot.)
   Remaining closed at maturity, or not opening along regular
   lines, as the acorn, or a cocoanut.
   [1913 Webster]