Houstonia: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus. 

	low plants
	leaves opposite, in pairs; NOT [leaves apparently whorled, the stipules resembling the leaves]

Rubiaceae: Answers to key questions in Budd's Flora  leading to this family. 

	herbs; NOT [shrubs or trees]
	plants green or with some chlorophyll; NOT [plants parasitic or saprophytic, without chlorophyll]
	plants without milky juice
	not climbing plants with tendrils
	leaves opposite; NOT [leaves basal or alternate]
	leaves with stipules, sometimes appearing whorled; NOT [leaves without stipules]
	flowers not in heads or spikes; NOT [flowers in long or short spikes], NOT [flowers in heads or in form resembling a head]
	flowers with two floral rings
	petals wholly or partly united forming a tube or bell
	stamens 4 or 5; NOT [stamens 3]
	ovary inferior; NOT [ovary superior]