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Chenopodium
See list of 16 species in this genusSize, orientation, surface patterns, and nature of the pericarp (e.g., adherent, loose) are all very important characters of the fruits. Most species of goosefoots have an adherent pericarp that covers the lustrous, often black, seed in fruit. Sometimes the shiny surface of the seed is visible in places where the pericarp has been abraded due to pressing and storage. This is very different from the utricle-type fruit where the pericarp loosens, splits, and small flakes or sheets detach from the seed. Though many species can be confidently identified while in flower, some groups of taxa require mature fruits for determination. Reference: Wahl (1954).
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1a. Fruits arranged vertically or both vertically and horizontally in the calyx; calyx with 3–5 sepals [Fig. 333]
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2a. Plants perennial from a thick, woody root system; leaf blades entire except for the basal pair of outwardly pointing lobes; achenes 1.5–2 mm wide; styles persistent on the fruit, 0.8–1.5 mm long; calyx with 4 or 5 sepals
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2b. Plants annual from a taproot; leaf blades dentate or serrate (sometimes ± entire in C. rubrum var. humile);
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3a. Principal leaf blades lanceolate to elliptic or oblong, conspicuously farinose on the abaxial surface; glomerules of flowers 1.8–2.5 mm wide; most fruits horizontally oriented, some vertically oriented [Fig. 333]
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3b. Principal leaf blades triangular to rhombic-ovate (rarely oblong), green or sparsely farinose on the abaxial surface; glomerules of flowers 2–12 mm wide; most or all fruits vertically oriented
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4a. Glomerules of flowers 2–5 mm wide; sepals at maturity herbaceous (somewhat fleshy in var. humile); horizontal seeds frequently present; vertical seeds with a basal radicle; plants coastal halophytes
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4b. Glomerules of flowers (3–) 5–12 mm wide; sepals at maturity fleshy; fruits all vertically oriented; horizontal seeds absent; vertical seeds with an apical radicle; plants inland weeds of forest openings and disturbed areas
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5a. Glomerules without subtending bracteal leaves (except sometimes the lower ones of each branch); seeds with convex sides, not grooved around periphery; flowers maturing from apex of inflorescence toward base
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5b. Glomerules subtended by bracts; seeds with a flattened groove around the periphery; flowers maturing from base of inflorescence toward apex
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6a. Sepals flat or with an inconspicuous keel on the abaxial surface, at maturity conforming to the outline of the fruit and the outline of the calyx appearing ± circular (except where individual sepals spread or reflex away from fruit) [Fig. 334]; stems, leaf blades, and sepals usually glabrous and green (plants sometimes sparsely farinose on some surfaces, especially when young)
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7a. Leaf blades entire, or rarely with a single tooth on each margin; stems quadrangular; sepals apiculate at the apex
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7b. At least the lower leaf blades with prominent teeth; stems terete to angled, but not quadrangular; sepals retuse or obtuse to acute at the apex, without an apiculus
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8a. Pericarp evidently separating from mature seed [Fig. 332]; leaf blades lanceolate to oblong-ovate, entire or with short, ascending teeth
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8b. Pericarp firmly attached to weakly separating from mature seed; leaf blades ovate or rhombic-ovate to triangular, sinuate-dentate to coarsely dentate
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9a. Flowers developing asynchronously (i.e., flowers and fruits will be present in the same glomerule until late season when only fruits are present); achenes 1.5–2.5 mm wide
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9b. Flowers developing synchronously (i.e., all the flowers in a glomerule of similar stage); achenes 1–1.5 mm wide
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10a. Achenes 1–1.2 mm wide, with rounded margins; inflorescence typically much longer and standing well above the principal foliage leaves
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10b. Achenes 1.2–1.5 mm wide, with acutely keeled margins; inflorescence typically shorter than to shortly exceeding the principal foliage leaves (in part)
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6b. Sepals keeled on the abaxial surface, not conforming to the fruit, the calyx appearing pentagonal or star-shaped [Fig. 328]; stems, leaf blades, and sepals moderately to densely farinose (foliage sometimes ± glabrous in forms of C. album)
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11a. Pericarp of mature fruits brown, minutely echinate (view at 20 ×), eventually separating and flaking away, leaving the lustrous, black seed [Fig. 332]
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12a. Leaf blades predominantly narrow-ovate, the larger usually wider than 10 mm and with some form of dentition or lobing; native plants of high-pH outcrops and woodlands
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12b. Leaf blades linear to lanceolate or oblong, (2–) 4–10 mm wide, entire to weakly lobed; naturalized plants of disturbed, often saline, soils
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11b. Pericarp of mature fruits pale to dark, smooth, irregularly roughened, or cellular-reticulate, remaining firmly attached to the seed [Figs. 330,335]
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13a. Achenes with acutely keeled margins; leaf blades irregularly dentate (in part)
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13b. Achenes with rounded margins; leaf blades entire to serrate or infrequently dentate
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14a. Principal leaf blades ± linear, 1–3 mm wide, with a single vein, entire; achenes 0.8–1 (–1.1) mm wide
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14b. Leaf blades narrow-lanceolate to rhombic, ovate, or triangular, 5–75 (–90) mm wide, pinnately veined, entire to, more commonly, toothed or lobed; achenes 0.9–2 mm wide
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15a. Achenes (1–) 1.3–2 mm wide, with a conspicuously cellular-reticulate pericarp [Fig. 330]; a minute style base (up to 0.2 mm long) sometimes present below the stigma branches
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15b. Achenes 0.9–1.5 (–1.6) mm wide, with a smooth or obscurely marked pericarp; style base absent, the 2 stigma branches sessile at the summit of the ovary
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16a. Sepals of many flowers spreading to reflexed at maturity, not covering the oval achene [Fig. 335]; lower leaf blades usually serrate with small, low teeth
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16b. Sepals curved over the orbicular achene and concealing it (rarely some flowers with exposed fruits) [Fig. 328]; lower leaf blades variable, usually prominently serrate or with tooth-like lobes
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Each photo represents one species in this genus.