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

	NOT [plants with a bluish tinge; flowers in dense globose heads; bracts spiny]
	NOT [leaves usually trifoliolate; leaflets palmate, 10-30 cm wide]
	foliage not spiny
	leaves (including lowest) divided into a few well-developed leaflets; NOT [leaves much divided, with leaflets or segments numerous];  NOT [leaves simple]
	leaves once pinnately divided, with more than 3 leaflets per leaf; NOT [leaves 2 or more times pinnate], NOT [foliage digitately compound]
	leaflets more than 2 mm wide; NOT [leaflets mostly 1-2 mm wide]
	leaflets linear to lanceolate, much longer than broad; NOT [leaflets elliptic to ovate to oblong in outline, twice as long as broad or less]
	leaflets serrate; NOT [leaflets entire]
	plants lacking axillary bulblets; NOT [plants with axillary bulblets largely replacing flowers]
	flowers white; NOT [flowers yellow]
	inflorescence not bluish
	fruit 2-3 mm long; NOT [fruit about 2 mm long], NOT [fruit 5-6 mm long]
	fruit generally 3 times as long as broad or less; NOT [fruit several times longer than broad]
	fruit oblong to elliptical; NOT [fruit linear to clavate]
	fruit not spiny; NOT [fruit covered with short, hooked spines]

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

	plants terrestrial or semiaquatic; NOT [plants aquatic, leaves submerged or floating]
	herbs; NOT [shrubs or trees]
	plants not with colored milky juice
	stems hollow
	plants with more than one normal leaf
	some or all leaves alternate; NOT [leaves opposite, whorled, or basal]
	leaves without stipules, or having glands; NOT [leaves with stipules]
	flowers in umbels
	parts of flowers mostly in fives; NOT [parts of flowers in twos or fours]
	flowers with two floral rings
	calyx regular; NOT [calyx irregular, some sepals smaller than others]
	each petal distinct from the others
	stamens 10 or fewer; NOT [stamens usually more than 10]
	styles 2; NOT [styles 5]
	ovary inferior; NOT [ovary superior]