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Viola key for chasmogamous flowering material
See list of 30 species in this subkey-
1a. Plants acaulescent, the leaves and peduncles arising directly from rhizomes or stolons [Figs. 933,936]
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2a. Petals entirely yellow; stipules entire; stigma essentially lacking a beak
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2b. Petals not entirely yellow, mostly purple, violet, or white; stipules ciliate, toothed, or lacerate on the margin; stigma with a conical, scoop-shaped, or hook-shaped beak
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3a. Style terminating in a slender, downward-oriented, hook-shaped beak; ovary (and later the capsule) pubescent
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3b. Style dilated at apex, terminating in a scoop-shaped or conical beak; ovary and capsule glabrous (capsule rarely pubescent in V. affinis)
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4a. Spur elongate, 4–10 mm long, 2 or more times as long as wide; flowers with purple, glabrous petals; stipules connate to the petioles
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5a. Leaf blades cordate-ovate to cordate-suborbicular, 0.8–1.3 times as long as wide, with a deep basal sinus, not decurrent on the petiole; spur 4–6 mm long
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5b. Leaf blades oblong to broad-lanceolate, becoming narrow-triangular to narrow-ovate post anthesis, 1.5–2.7 times as long as wide, broad-cuneate to subcordate at the base, decurrent on the petiole; spur 5–10 mm long
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4b. Spur shorter, up to 3.2 mm long and less than 2 times as long as wide; flowers with purple or white petals, when purple then at least the lateral petals pubescent; stipules distinct
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6a. Flowers relatively smaller, mostly 7–12 mm long, with white petals (pale blue in one alpine species); rhizomes slender, mostly less than 3 mm thick, usually horizontal; stolons produced, at least by summer (not produced in V. renifolia)
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7a. Leaf blades 1.5–7 times as long as wide, narrow-cuneate to subcordate at the base
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8a. Leaf blades 3–7 times as long as wide, narrowly tapering at the base, the margins denticulate, each tooth with a distinct red-brown to black gland at the apex
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8b. Leaf blades 1.5–2.5 times as long as wide, broader at the base, widely tapering to truncate or subcordate at the base, the margins crenate, the teeth with inconspicuous, pale glands
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7b. Leaf blades up to 1.5 times as long as wide, cordate at the base
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9a. Corolla violet or at least tinged with violet; lateral petals sparsely pubescent; plants restricted to alpine areas over 900 m elevation
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9b. Corolla white; lateral petals glabrous or pubescent;
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10a. Leaf blades low-crenate or subentire along the margins, thin, strictly glabrous
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10b. Leaf blades low-serrate along the margins, thicker, commonly with some pubescence (sometimes glabrous in V. renifolia with characteristically wide leaves––see description)
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11a. Leaf blades cordate-orbicular to reniform, the midrib usually equaling 50–77 percent of the total blade width; stolons not produced; pubescence variable, but when restricted to a single side of the blade, then found only on the abaxial (i.e., lower) surface
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11b. Leaf blades broad cordate-ovate (to cordate-orbicular), the midrib usually equaling 75–90 percent of the total blade width; stolons present, at least later in season; pubescence variable, but when restricted to a single side of the blade, then found only on the adaxial (i.e., upper) surface
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6b. Flowers relatively larger, mostly 13–22 mm long, with purple petals (rare albino forms said to exist); rhizomes stouter, mostly 4–6 mm thick, usually ascending; stolons not produced
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12a. Leaf blades with conspicuous lobes (though the first leaves to appear in V. palmata are unlobed) [Figs. 933,938]
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13a. Leaf blades oblong-lanceolate to ovate-triangular, 1.5–3 times as long as wide, coarsely serrate to divided into short lobes at the base [Fig. 936]; lobes, if present, less than 50% of the total length of the leaf blade (in part)
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13b. Leaf blades ± ovate in outline, less than 1.5 times as long as wide, with evident lobes (except for the first leaves to emerge which may be unlobed to weakly lobed); lobes often greater than 50% of the total length of the leaf blade
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14a. Lateral petals glabrous; style lacking a beak, with an asymmetrical concave summit; corolla rotate (i.e., wide open), the stamens clearly visible; corolla either bicolorous with the upper two petals dark purple or concolorous and all the petals light violet
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14b. Lateral petals pubescent on inner surface; style with a conical beak on the lower side of the expanded apex; corolla only distally spreading, the stamens somewhat concealed; corolla concolorous with violet to purple petals
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12b. Leaf blades all unlobed
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17a. Leaf blades 1.5–3 times as long as wide, cuneate to subcordate at the base, often more coarsely serrate or even somewhat lobed at the base of the blade (especially in later season leaves) [Fig. 936] (in part)
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17b. Leaf blades commonly less than 1.75 times as long as wide, definitely cordate at the base, the teeth at the base of the blade no more obvious than those along the middle of the blade margin (except in V. pectinata)
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18b. Hairs of three lower petals longer than 1 mm and tapering to broadly rounded the apex [Fig. 932]; spurred petal sparsely pubescent (rarely glabrous in V. sororia) [Fig. 932]
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19a. Sepals ciliate (sometimes eciliate in V. hirsutula) [Fig. 937]; leaf blades usually as wide as or wider than long and pubescent
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20a. Pubescence of leaves consisting of silver hairs concentrated on the adaxial surface, the abaxial surface and petioles glabrous or nearly so; leaves usually rounded at apex, often suffused with purple abaxially
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20b. Pubescence of leaves variable, but not concentrated on the adaxial surface and often found on the petioles; leaves rounded, to more commonly, obtusely to acutely pointed at apex, without purple coloration
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19b. Sepals eciliate [Figs. 930,934]; leaf blades either conspicuously longer than wide or essentially glabrous or both
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22a. Leaf blades triangular at chasmogamous anthesis, becoming broad-triangular, later with prominent, coarse teeth near the basal margins that gradually become shorter and narrower toward the apex
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22b. Leaf blades narrow-ovate, with rather uniform teeth along the margin
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21b. Sepals ovate to narrow-ovate or ovate-oblong, obtuse to rounded at apex [Fig. 937]
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23a. Leaf blades longer than wide, often narrow cordate-ovate to triangular; lateral petals spreading, the flowers wide open in life; leaves commonly pubescent
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23b. Leaf blades as wide as or wider than long, often broad-cordate-ovate; lateral petal directed forward, the flowers narrow in life; leaves glabrous
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1b. Plants with leafy aerial stems, the peduncles arising from the axils of leaves [Fig. 935]
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24a. Plants annual, with taproots; stipules foliaceous, prominently lobed in pinnatifid fashion; style dilated upward into a globose, hollow stigma with a wide orifice on the lower side
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25a. Flowers longer than 15 mm; petals exceeding the sepals by 2 mm or more; corolla variously colored, often yellow-white or yellow-orange with a yellow center and the upper petals dark blue on the apical half or sometimes dark blue throughout with a yellow center
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25b. Flowers up to 10 mm long; petals shorter than the sepals or up to 2 mm longer than the sepals; corolla variously colored, often yellow-white with a yellow center
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24b. Plants perennial from rhizomes; stipules scarious to herbaceous, entire to toothed or lacerate [Fig. 935]; style either slender at the apex or capitate, but not globose
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26a. Petals white to cream or violet to purple, the lateral ones pubescent with hairs that taper to the apex (glabrous in V. rostrata); spur 3–18 mm long, usually 2 or more times as long as wide; style slender throughout or only slightly widened apically, not capitate, bent at the apex (straight in V. rostrata)
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27a. Petals white to cream; sepals ciliate
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27b. Petals violet to purple; sepals eciliate
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28a. Spur 8–15 mm long; lateral petals glabrous; style ± straight
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28b. Spur 2.8–7 mm long; lateral petals pubescent on inner surface; style bent near tip
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29a. Leaf blades commonly with sparse to dense pubescence, the hairs never restricted to the adaxial surface, the upper blades ovate to triangular-lanceolate and mostly truncate at the base; petioles distinctly winged; style slightly expanded apically, terminating in a stout, bent tip as long as the diameter of the style
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29b. Leaf blades commonly glabrous, when pubescent the hairs restricted to the adaxial surface, the upper blades usually ovate to orbicular, with a cordate base; petioles not distinctly winged; style of nearly uniform diameter throughout, terminating in a bent tip nearly twice as long as the diameter of the style
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26b. Petals yellow or white with yellow at the base, the lateral ones pubescent with hairs that are dilated and rounded or knob-shaped at the apex; spur less than 2 mm long and less than 2 times as long as wide; style capitate at the apex
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30a. Petals entirely yellow; stipules herbaceous, green
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30b. Petals white with a yellow base, tinged with purple on the outside; stipules scarious or subscarious, pale
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Show photos of:
Each photo represents one species in this subkey.