Key 1

1	Pistillate flowers of 2 kinds: some with calyx 3-5-lobed and seed horizontal, others lacking perianth, enclosed in pair of bracteoles, seed vertical; fruiting bracteoles samaralike, strongly compressed, oval to orbicular or ovate; plants widespread in North America [20a.1. Atriplex sect. Atriplex]		1 Atriplex hortensis
+	Pistillate flowers all alike or, if dimorphic, both kinds lacking perianth, enclosed within bracteoles, and seed vertical; fruiting bracteoles variously compressed (orbicular in A. heterosperma)		(2)
2 (1)	Bracteoles ± thickened with spongy tissue, especially toward base [20a.2. Atriplex sect. Teutliopsis]		(3)
+	Bracteoles not thickened (except A. joaquiniana)		(7)
3 (2)	Lower leaves linear or ovate-lanceolate, sometimes toothed and/or with proximalmost lobe largest, but then not triangular, or if so leaves thick textured		(4)
+	Lower leaves (sometimes all or most) triangular and thin textured		(5)
4 (3)	Leaves linear to lanceolate or oblong, thin, green or slightly scurfy when young; seeds ovoid, not wider than long; coastal e Canada and ne United States, w disjunctly to Pennsylvania, Ohio, and Indiana		2 Atriplex littoralis
+	Leaves ovate-lanceolate or linear, or triangular or triangular-hastate, typically thickened and ± scurfy, even in age; seeds ellipsoid, wider than long; broad distribution from coastal e Canada and United States, and c and w United States		8 Atriplex dioica (in part)
5 (3)	Bracteoles, some or all, short stipitate, margin irregularly denticulate to laciniate, lateral angles of faces usually developed into 1-3 teeth; Cape Breton coast, Newfoundland, Nova Scotia, and New Brunswick		10 Atriplex glabriuscula (in part)
+	Bracteoles all sessile, margin entire or slightly toothed, lateral angles shortly pointed but not definitely toothed; geography below		(6)
6 (5)	Inflorescence with leafy bracts to the tip, glomerules loose, irregularly spaced; bracteoles thick spongy, margin united to middle; seeds 2.5+ mm wide, usually not distinctly dimorphic, dark brown to black, irregularly biconvex; radicle median, ± antrorse; coastal e United States, from New Jersey n to Maine and Nova Scotia and n to Newfoundland and Labrador, and w disjunctly to Hudson Bay and n Alberta		10 Atriplex glabriuscula (in part)
+	Inflorescence with leafy bracts only at base, glomerules tight, contiguous or irregularly spaced; bracteoles thin to slightly thickened and spongy, margin united only at base; seeds mostly less than 2.5 mm wide, usually distinctly dimorphic, mostly small and glossy black, but also some larger, and dull brown, flattened and disc-shaped; radicle subbasal, obliquely antrorse to spreading; plant a weedy introduction of broad distribution in United States and s Canada		9 Atriplex prostrata
7 (2)	Plants mostly less than 1.2 dm; proximal leaves lanceolate to rhombic-ovate, bases cuneate to attenuate; bracteoles rhombic-ovate, thin herbaceous or membranaceous, entire, free to base; seeds black, lustrous, biconvex, 1.2-2.5 mm wide, with subbasal, spreading radicle; plants in the sublittoral zone on coasts of Newfoundland		11 Atriplex nudicaulis
+	Plants mostly more than 1.2 dm; proximal leaves, bracteoles, and seeds not simultaneously as above; distribution various		(8)
8 (7)	Fruiting bracteoles ovate to elliptic or orbiculate-cordate		(9)
+	Fruiting bracteoles never orbiculate-cordate, frequently toothed, usually with lateral angles		(11)
9 (8)	Bracteoles ovate to widely triangular, surfaces often 2-tuberculate, margin toothed; leaves usually thickened, ± scurfy, even at maturity		8 Atriplex dioica (in part)
+	Bracteoles orbiculate-ovate, surfaces smooth, margin entire; leaves usually thin, green on both sides, not or scarcely scurfy		(10)
10 (9)	Leaves broadly triangular-hastate; widely distributed from Quebec, w to Brit- ish Columbia and s to California, Nevada, Utah, and Colorado		7 Atriplex heterosperma
+	Leaves mostly lanceolate to narrowly hastate; s British Columbia, adjacent Alberta, and South Dakota		4 Atriplex oblongifolia (in part)
11 (8)	Bracteoles (2-)2.5-3(-4.5) mm; leaf blades deltoid to rhombic-ovate or oblong-ovate, coarsely toothed; saline soils in Sacramento Valley and east San Francisco Bay vicinity and San Joaquin Valley, California		6 Atriplex joaquiniana
+	Bracteoles mainly 4-10+ mm; leaf blades hastate or entire, lanceolate to oblong; coastal salt marshes or ruderal weedy species of broad distribution		(12)
12 (11)	Largest bracteoles strap-shaped or ovate-lanceolate; halophytes of w and nw coastal areas of North America		5 Atriplex gmelinii
+	Largest bracteoles ovate, ovate-triangular, or rhombic; e coastal North America (disjunctly westward) or widespread ruderal weeds		(13)
13 (12)	Radicle of brown seeds basal and spreading; e coastal salt marshes and disjunctly w to Hudson Bay and n Alberta		10 Atriplex glabriuscula (in part)
+	Radicle of brown seeds subbasal to median and antrorse; widespread ruderal weeds		(14)
14 (13)	Bracteoles rhombic, margin united almost to middle, lateral angles definite; terminal inflorescence with densely compressed, ± uniform- sized bracteoles; distal leaves green on both sides		3 Atriplex patula
+	Bracteoles ovate or triangular-ovate, margin free to base, lateral angles lacking; terminal inflorescence with loosely spaced, larger and smaller bracteoles; distal leaves whitish abaxially		4 Atriplex oblongifolia (in part)