The Collaborative International Dictionary of English v.0.48:

Lobeliaceous \Lo*be`li*a"ceous\, a. (Bot.)
   Of or pertaining to a natural order of plants of which the
   genus Lobelia is the type.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lobeliaceous
    adj 1: belonging to the family Lobeliaceae