1	Seeds vertical or both horizontal and vertical; leaf blades glabrous or occasionally farinose (C. glaucum, C. macrospermum) [7a. Chenopodium subg. Blitum]		(2)
+	Seeds all horizontal; leaf blades usually farinose [7b. Chenopodium subg. Chenopodium, 7b.2 Chenopodium sect. Chenopodium and 7b.1 sect. Grossefoveata]		(9)
2 (1)	Perianth segments 5; plants perennial [7a.1. Chenopodium sect. Agathophytum]		(3)
+	Perianth segments usually 3; plants annual		(4)
3 (2)	Leaf blade margins entire		1 Chenopodium bonus-henricus
+	Leaf blade margins sinuate-dentate		2 Chenopodium californicum
4 (2)	Leaf blades lanceolate or oblong, glaucous abaxially [7a.5 Chenopodium sect. Glauca]		8 Chenopodium glaucum
+	Leaf blades triangular or rhombic, rarely lanceolate, green abaxially		(5)
5 (4)	Leaf blades farinose abaxially [7a.3. Chenopodium sect. Degenia]		5 Chenopodium macrospermum
+	Leaf blades glabrous abaxially		(6)
6 (5)	Glomerules 3-10 mm diam., sessile on unbranched terminal and occasionally axillary spikes; perianth segments fleshy, red at maturity (not fleshy but often red in C. capitatum var. parvicapitatum); seeds all vertical [7a.2. Chenopodium sect. Blitum]		(7)
+	Glomerules 2-5 mm diam., sessile on lateral branched spikes; perianth segments membranaceous, green at maturity; horizontal and vertical seeds both present [7a.4. Chenopodium sect. Pseudoblitum]		(8)
7 (6)	Glomerules not subtended by leaflike bracts in distal 1/2 of spike; flow- ers maturing uniformly from apex of plant to base		3 Chenopodium capitatum
+	Glomerules subtended by leaflike bracts throughout inflorescence; flow- ers maturing from base of plant to apex		4 Chenopodium foliosum
8 (6)	Perianth segments connate nearly to tip		6 Chenopodium chenopodioides
+	Perianth segments mostly connate only at very base		7 Chenopodium rubrum
9 (1)	Flowers individually disposed in panicles; leaf blades glabrous		(10)
+	Flowers in loose or dense glomerules; leaf blades usually farinose [7b.2. Chenopodium sect. Chenopodium]		(11)
10 (9)	Leaves sinuate-dentate; seeds 1.3-1.9 mm diam. [7b.1. Chenopodium sect. Grossefoveata]		9 Chenopodium simplex
+	Leaves entire; seeds 0.8-1.3 mm diam. [7b.2a. Chenopodium subsect. Polysperma]		10 Chenopodium polyspermum
11 (9)	Primary leaves linear, linear-lanceolate, or occasionally narrowly oblong-ovate, 2-3 times longer than broad or longer; usually without teeth or lobes or occasionally with a pair of basal lobes [7b.2d. Chenopodium subsect. Leptophylla and 7b.2b. Chenopodium subsect. Chenopodium (33. C. strictum)]		(12)
+	Leaves ovate, rhombic, triangular, or lanceolate, to 2 times longer than broad; usually with basal lobes and often with additional teeth on margin		(22)
12 (11)	Leaves with 1 vein, blades linear, usually somewhat fleshy, margins entire		(13)
+	Leaves with 3 veins from base, blades linear, lanceolate, or occasionally narrowly oblong-ovate or triangular-rhombic, usually without teeth or lobes or occasionally with a pair of basal lobes		(16)
13 (12)	Fruit an utricle, pericarp separable; plant mostly not farinose		18 Chenopodium subglabrum
+	Fruit an achene, pericarp attached; plant mostly farinose		(14)
14 (13)	Sepals connate to or above widest part of seed; seeds 1.3-1.5 mm diam., margins acute		17 Chenopodium cycloides
+	Sepals connate only at very base; seeds 0.8-1.5 mm diam., margin srounded		(15)
15 (14)	Seeds 1.4-1.6 mm diam.; well-grown plants more than 4 dm		19 Chenopodium pallescens
+	Seeds 0.9-11.1 mm diam.; plants chiefly less than 4 dm		20 Chenopodium leptophyllum
16 (12)	Leaves 3 times longer than broad or longer		(17)
+	Leaves 2-3 times longer than broad, usually narrowly oblong-ovate or deltoid rhombic		(20)
17 (16)	Fruit an achene, pericarp attached, minutely granular-roughened; seeds flattened on top		16 Chenopodium hians
+	Fruit an utricle, pericarp separable; seeds rounded on top		(18)
18 (17)	Perianth spreading from fruit at maturity; plants strictly erect		13 Chenopodium pratericola
+	Perianth enclosing fruit at maturity; plants erect to spreading		(19)
19 (18)	Plants usually spreading; perianth segments obtuse; leaf blades usually unlobed		14 Chenopodium desiccatum
+	Plants erect; perianth segments acute; leaf blades often with basal lobes		15 Chenopodium foggii
20 (16)	Fruit an utricle, pericarp separable; leaf blades entire		21 Chenopodium atrovirens (in part)
+	Fruit an achene, pericarp attached; leaf blades often toothed		(21)
21 (20)	Leaves with 3 prominent veins, sparsely farinose; seeds 0.7-0.8 mm diam		25 Chenopodium nevadense (in part)
+	Leaves with one prominent vein and two obscure outer veins at the base, moderately farinose; seeds 0.9-1.5 mm diam.		33 Chenopodium strictum (in part)
22 (11)	Seeds honeycomb-pitted [7b.2f. Chenopodium subsect. Favosa]		(23)
+	Seeds smooth or areolate		(26)
23 (22)	Lower leaves entire or with only 1-2 teeth or lobes near base		(24)
+	Lower leaves serrate and usually lobed		(25)
24 (23)	Seeds subglobose, entirely covered by perianth segments at maturity; pericarp slightly to prominently whitened; leaves broadest very near base		26 Chenopodium watsonii
+	Seeds more or less flattened, partially exposed at maturity; pericarp black; leaves usually prominently lobed above the base		27 Chenopodium neomexicanum
25 (23)	Leaves with central lobe 2-3 times longer than lateral lobe		28 Chenopodium ficifolium
+	Leaves with central lobe only slightly longer than lateral lobes or unlobed and merely toothed		29 Chenopodium berlandieri
26 (22)	Leaves triangular		(27)
+	Leaves ovate to broadly ovate, rhombic, or lanceolate, variously lobed or toothed		(30)
27 (26)	Leaf blades toothed and sometimes with basal lobes, usually glabrous		(28)
+	Leaf blades with basal lobes but no additional teeth, usually farinose [7b.2e. Chenopodium subsect. Fremontiana]		(29)
28 (27)	Seeds 0.8-1.2 mm diam, seed margin round; leaf blades often with basal lobes [7b.2b. Chenopodium subsect. Urbica]		11 Chenopodium urbicum
+	Seeds 1-1.5 mm diam., seed margin acute; leaf blades without basal lobes [7b.2c. Chenopodium subsect. Undata]		12 Chenopodium murale
29 (27)	Plants simple below, branching above; seeds 1-1.3 mm diam.		22 Chenopodium fremontii
+	Plants profusely branching from base; seeds 0.9-1.1(-1.2) mm diam		23 Chenopodium incanum
30 (26)	Leaf blades without teeth except for often present basal lobes or teeth		(31)
+	Leaf blades with lateral teeth and often basal lobes		(35)
31 (30)	Flowers in markedly different stages of development in the same glom- erules [7b.2g. Chenopodium subsect. Standleyana]		30 Chenopodium standleyanum
+	Flowers all more or less in same stages of development in same glomerules		(32)
32 (31)	Leaves without basal lobes or teeth, malodorus [7b.2b. Chenopodium subsect. Chenopodium]		34 Chenopodium vulvaria
+	Leaf blades with basal lobes; not malodorous		(33)
33 (32)	Fruit an achene, pericarp attached [7b.2e. Chenopodium subsect. Fremontii]		25 Chenopodium nevadense (in part)
+	Fruit an utricle, pericarp separable		(34)
34 (33)	Plants 0.1-0.7 m [7b.2d. Chenopodium subsect. Leptophylla]		21 Chenopodium atrovirens (in part)
+	Plants 0.5-1.2 m [7b.2e. Chenopodium subsect. Fremontii]		24 Chenopodium albescens
35 (30)	Leaves widely ovate, as long as broad; lateral lobes equaling terminal lobes in size		31 Chenopodium opulifolium
+	Leaves ovate, rhombic, or lanceolate, longer than broad; lateral lobes when present smaller than the terminal lobe		(36)
36 (35)	Leaf margins tapering to an acute apex; leaves ovate, rhombic, or lanceolate; inflo- rescence branched spicate or cymose		32 Chenopodium album
+	Leaf margins more or less parallel below the obtuse apex, leaves lanceolate to narrowly elliptic; inflorescence normally moniliform, not profusely branching		33 Chenopodium strictum (in part)