|  | herbs; NOT [shrubs or trees] | 
      |  | land plants; NOT [water plants] | 
      |  | plants NOT parasitic on trees (plants
        rooted in soil or water); NOT [plants parasitic on branches of trees] | 
      |  | plant cushion-like | 
      |  | leaves opposite; NOT [leaves alternate] | 
      |  | leaves with stipules free or sheathing
        the stem; NOT [leaves without stipules] | 
      |  | stipules membranous; NOT [stipules
        forming a sheath above nodes] | 
      |  | flowers with only one floral ring, with
        sepals but not petals | 
      |  | stamens and pistils in each flower; NOT
        [stamens or pistils in separate flowers on the same plant] | 
      |  | plants with stems or stemless, but with
        more than one pair of leaves; NOT [plants stemless with a single pair of
        large reniform leaves, calyx 3-lobed] |