This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Annual or perennial, green and glabrous, white-mealy or glandular-pubescent herbs, with alternate petioled entire sinuate-dentate or pinnately lobed leaves. Flowers very small, green, perfect, sessile, bractless, clustered in axillary or terminal, often panicled or compound spikes. Calyx 2-5-parted or 2-5-lobed, embracing or enclosing the utricle, its segments or lobes herbaceous or slightly fleshy, often keeled or ridged. Stamens 1-5; filaments filiform or slender. Styles 2 or 3; seed horizontal or vertical, sometimes in both positions in different flowers of the same plant, firmly attached to or readily separable from the pericarp; endosperm mealy, farinaceous; embryo completely or incompletely annular. [Greek, goose-foot, from the shape of the leaves.]
About 60 species, mostly weeds, of wide geographic distribution. Besides the following, some 5 others occur in the western parts of North America. Type species: Chenopodium rubrum L.
* Embryo a complete ring; plants not glandular.
Leaves white-mealy on the lower surface (except in some races of No. 1).
Leaves or some of them mostly sinuate-toothed or lobed.
Sepals strongly keeled in fruit.
Pericarp firmly attached to the seed; stem erect, tall.
Pericarp readily detached from the seed; stem low.
Sepals not keeled in fruit; stem decumbent.
Leaves mostly entire.
Leaves linear to oblong, short-petioled.
Leaves broadly ovate, long-petioled.
Leaves green and glabrous or nearly so on both surfaces when mature.
Leaves oblong or ovate-oblong, entire.
Leaves, at least the lower, sinuate, toothed or incised.
Stamens 5; calyx not fleshy.
Pericarp readily separable from the seed.
Leaves oblong or lanceolate; calyx-lobes scarcely keeled.
Leaves triangular-hastate; calyx-lobes keeled.
Pericarp firmly attached to the seed.
Flower-clusters, at least the upper, longer than the leaves.
Spikes loosely panicled in the axils, the panicles shorter than the leaves.
Stamens only 1 or 2; calyx slightly fleshy, red.
Leaves very coarsely 2-6-toothed.
Leaves broadly triangular-hastate, entire or merely undulate.
** Embryo an incomplete ring; plants glandular aromatic.
Leaves ovate or oblong, pinnately lobed; flowers in long loose panicles.
Leaves lanceolate; flowers in continuous or interrupted spikes.