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Cardamine
See list of 15 species in this genusSome species of Cardamine are frequently treated as nothospecies (e.g., C. incisa, C. maxima), with the often-cited reasons of morphological intermediacy and failure to produce mature fruits in some populations. It is important to note that these plants are not exactly intermediate (i.e., they have character states that are novel or extreme compared with the putative parents; Sweeney and Price 2001) and often produce fertile siliques. Further, some of the populations occur great distances from where the parental taxa are sympatric. These observations suggest that these taxa, which are quite possibly derived through hybridization, are acting as species and are treated as such here. References: Sweeney and Price (2001), Al-Shehbaz et al. (2010).
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1a. Principal leaf blades palmately lobed or palmately divided into 3–5 segments; stems gradually narrowing at base to a fragile junction with a swollen, fleshy rhizome; siliques with a persistent style beak 5–8 mm long
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2a. Rhizome lacking tooth-like projections or these very obscure, formed of segments joined by fragile connectives, the rhizome readily breaking into segments [Fig. 511]; stem above the leaves usually pubescent with spreading hairs; stems usually with 3 leaves in a single whorl
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2b. Rhizome with tooth-like projections, either continuous [Fig. 513] or with alternately enlarged and constricted areas, but not readily breaking into segments; stem above the leaves usually glabrous; stems with usually 2 opposite leaves or with 3 alternate leaves
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3a. Cilia on leaf margin mostly 0.2–0.3 mm long and spreading; rhizome alternately enlarged and constricted
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3b. Cilia on leaf margin mostly 0.1 mm long and ascending or appressed; rhizome continuous or alternately enlarged and constricted
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4a. Leaflets sessile; rhizome alternately enlarged and constricted
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4b. Leaflets usually petiolulate; rhizome continuous [Fig. 513]
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1b. Principal leaf blades simple or pinnately lobed or pinnately divided [Figs. 512,514,515]; stems arising from caudices, taproots, or rhizomes, when arising from rhizomes the stem widest at base and narrowing upward and/or continuous with rhizome; siliques with a persistent style beak 0.3–6 mm long
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5a. Lower leaf blades, as well as usually the upper, simple
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6a. Petals up to 5 mm long or absent; fruiting pedicels 1–10 mm long; stems arising from a vertical taproot and caudex or fibrous roots
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7a. Petals absent or up to 1.2 mm long and concealed by the sepals; siliques 5–12 mm long, spreading to ascending [Fig. 512]; fruiting pedicels 1–3 mm long; wetland and aquatic plants, primarily of fresh-tidal river shores (in part)
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7b. Petals 3–5 mm long, visible; siliques 15–35 mm long, erect; fruiting pedicels 4–10 mm long; dwarf alpine plants
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6b. Petals 7–16 mm long; lower fruiting pedicels 20–30 mm long; stems arising from a stout, tuber-like rhizome
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8a. Sepals green turning yellow; petals white (rarely pink); stem glabrous or pubescent with appressed hairs shorter than 0.15 mm; stems mostly 20–40 cm tall to the first pedicel
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8b. Sepals purple turning brown; petals pink to purple (rarely white); stem pubescent with spreading hairs 0.2–0.8 mm long; stems mostly 8–20 cm tall to the first pedicel
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5b. Lower leaf blades, as well as usually the upper, pinnately divided or pinnately lobed with sinuses extending nearly to the midrib
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9b. Principal leaf blades with 5–17 leaflets [Figs. 514,516]; siliques 10–30 mm long; lower fruiting pedicels (4–) 5–18 mm long; petals 1.5–4 mm long, visible (sometimes absent in C. impatiens)
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10a. Stem leaves sagittate-auriculate, with sharply toothed to lacerate-margined leaflets that are usually acuminate at the apex [Fig. 514]; petals absent or present and 2–3 mm long, scarcely exceeding the sepals
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10b. Stem leaves shortly petiolate, not auriculate, with entire to crenate-dentate leaflets that are rounded to acute at the apex [Fig. 516]; petals present, 1.5–15 mm long
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11a. Petals 8–15 mm long; styles 3–6 mm long; lower fruiting pedicels 12–18 mm long; plants perennial
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12a. Primary veins of terminal leaflet of basal leaves terminating in a ± triangular, callus tip that is prominently excurrent beyond the leaflet blade tissue [Fig. 516]; petals pink to white in life, drying pink to pink-purple; leaflets of upper stem leaves commonly sessile
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12b. Primary veins of terminal leaflet of basal leaves terminating in a callus region, but the callus either not excurrent beyond the leaflet blade tissue or scarcely excurrent as a semicircular (i.e., dome-shaped) tip [Fig. 512]; petals white in life, drying white, cream, yellow-white, or brown-white; leaflets of upper stem leaves commonly petiolulate
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11b. Petals 1.5–4 mm long; styles 0.3–1.5 mm long; lower fruiting pedicels (3–) 5–14 mm long; plants annual or biennial (sometimes short-lived perennial in C. flexuosa)
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13a. Basal leaves numerous, persistent, with hirsute petioles; stems with 2–5 (–6) leaf-bearing nodes; flowers with 4 stamens; siliques usually erect and parallel or nearly so to the raceme axis
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13b. Basal leaves few, sometimes absent at anthesis, with glabrous petioles (always with hirsute petioles in C. flexuosa, a very rare introduction); stems with 4–10 (–20) leaf-bearing nodes; flowers with 6 stamens (some individuals rarely with only 4 stamens); siliques usually erect-ascending to ascending and not parallel to the raceme axis (except sometimes in C. parviflora)
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14a. Stems glabrous; stem leaves mostly 20–40 mm long, with linear to oblanceolate lateral leaflets or segments that are neither petiolulate nor decurrent on the leaf rachis; styles 0.5–1 mm long; seeds 0.7–0.9 mm long
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14b. Stems usually at least sparsely hispid near the base (except in inundated plants); stem leaves mostly 40–100 mm long, with oblong to suborbicular lateral leaflets or segments that are either petiolulate or decurrent on the leaf rachis; styles (0.3–) 0.5–2 mm long; seeds (0.9–) 1–1.5 mm long
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15a. Lateral leaflets or segments of stem leaves decurrent on leaf rachis; petioles glabrous; stems erect, not flexuous; native plant of shorelines and wetlands
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15b. Lateral leaflets or segments of stem leaves not decurrent on leaf rachis; petioles usually hirsute; stems flexuous, sometimes decumbent-based; introduced plants primarily of human-disturbed places
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Each photo represents one species in this genus.