Source : Webster's Revised Unabridged Dictionary (1913)

Stemless \Stem"less\, a.
   Having no stem; (Bot.) acaulescent.

Source : WordNet®

stemless
     adj 1: not having a stem; "stemless glassware" [ant: {stemmed}]
     2: having no apparent stem above ground [syn: {acaulescent}]
        [ant: {caulescent}]