Keys to Nature
Project
Key to the "Stemless Blue" Violets, Subsection Boreali-Americanae, of the Chicago Region - Expert Version


© Nir L. Gil-ad, Viola sagittata - Keys to Nature Project

Title:
Key to the "Stemless Blue" Violets, Subsection Boreali-Americanae, of the Chicago Region - Expert Version
Revisions:
156
Author(s):
Nir L. Gil-ad
Email:
nir.l.gil.ad@gmail.com, jkluse@fieldmuseum.org
Description:
The key has been constructed in order to assist you in identifying the "stemless blue" violets - Viola subsection Boreali-Americanae (W. Becker) Gil-ad - that occur in the Chicago Region, and covers both spring and summer plants. The spring plants bear chasmogamous - outcrossing showy - flowers, and the summer plants bear cleistomagous - reduced, apetalous, closed, highly fertile - flowers that self-fertilize without opening. Both types of flowers produce capsules and seeds. The key is based on the comprehensive treatment of the subsection published in the following publications: Gil-ad, N.L. 1997. Systematics of Viola subsection Boreali-Americanae. Boissiera 53: 1-130. Gil-ad, N.L. 1998. The micromorphologies of seed coats and petal trichomes of the taxa of Viola subsect. Boreali-Americanae (Violaceae) and their utility in discerning orthospecies from hybrids. Brittonia 50: 91-121. Please note that the members of the subsection are characterized by relative paucity of variability in macromorphological characters and lack of significant gaps between character states. Furthermore, hybridization, followed in some localities by introgression, is very frequent among the members. The key will assist you in identifying orthospecies, but you should be aware that some introgressants will readily key out to orthospecies if their deviation from an orthospecies is only slight and undetectable with the characters used. Any plant deviating in one or more characters should be suspected as a hybrid. Accordingly, it is important that you make the effort to match and contrast all the characters and habitat data in the two leads of each couplet with those of the plant you are trying to identify. Synonyms and published combinations of albinos, putative hybrids and putative introgressants of Viola subsection Boreali-Americanae are listed in Boissiera 53: 113-116. Viola septentrionalis Greene is not currently known from the Chicago Region, as circumscribed by the vPlants Project. However, on the basis of herbarium records from adjacent counties in Wisconsin as well as the literature it may be found there in the future. ACKNOWLEDGEMENTS: Thanks are due to the Curators and staff of F, UWM, and WIS for searching for specimens of Viola septentrionalis. NOTE: Please pardon the overly simplified formatting of the text. Future programming on the Keys to Nature website plans to alleviate this.

START THIS KEY

Key Structure:
1a. Plants bearing chasmogamous (outcrossing showy) flowers in the spring - 2.
1b. Plants bearing cleistomagous (reduced, apetalous, closed) flowers in the summer - 11.

2a. Blades undivided and unlobed (including uncleft and unlobed above base) - 3.
2b. Blades divided or both reniform and trilobed - 10.

3a. Trichomes borne on the lower lateral petals and the spurred petal - 4.
3b. Trichomes borne only on the lower lateral petals - 8.

4a. Peduncles glabrous; sepals eciliate - 5.
4b. Peduncles pubescent; sepals densely ciliate or +/- ciliate on the upper half - 7.

5a. Blades more than two times longer than wide, elliptic to oblong-lanceolate, base subtruncate or hastate - V. sagittata
5b. Blades less than two times longer than wide, cordate to reniform or narrowly ovate, base cordate - 6.

6a. Blades cordate to reniform, apex obtuse, apical angle of the largest blades 100 -145 degrees; upper lateral petals 3-4 mm wide, narrower than the lower lateral petals; lateral petals tapering to almost clawed base; apex of spurred petal emarginate; plants growing on calcareous loam in cool, shaded wet banks of slow streams, rivers, and lakes or wet soil pockets of protected rock crevices - V. nephrophylla
6b. Blades narrowly ovate, apex acute to rounded, apical angle of the largest blades 60-85 degrees; upper lateral petals 5-7 mm wide, wider than the lower lateral petals; lateral petals not tapering to almost clawed base; apex of spurred petal rounded to subtruncate; plants growing on rich loam in low shady borders of lakes and streams and low woods, wet thickets and meadows - V. affinis

7a. Peduncle long: 5-12 cm long; blades broadly ovate to cordate, length/width ratio of the largest blades 1-1.3, margins crenate-serrate; sepals densely ciliate, apex obtuse; spurred petal 12-21 mm long (including the spur); spur 2-3 mm long; plants growing on loam, often mixed with coniferous litter, in openings in coniferous woods, open groves of Thuja occidentalis, open mixed woods - V. septentrionalis
7b. Peduncle short: 2-4 cm long; blades widely ovate to ovate-oblong, length/width ratio of the largest blades 1.5-1.8, margins crenulate; sepals +/- ciliate on the upper half, apex acute; spurred petal 10-15 mm long (including the spur); spur 1-2 mm long; plants growing on gravelly soil or coarse sand in open Quercus forests, edges of forests and forest roads - V. fimbriatula

8a. Petal trichomes clavate and short; blades light green; plants of swamps, bogs, wet meadows, rock crevices in slow streams; roots often submerged in soaked muck, dark humus or Sphagnum mats - V. cucullata
8b. Petal trichomes cylindrical and long or only slightly expanded at the apex; blades dark green; plants of drier habitats; roots not submerged in a soaked substrate - 9.

9a. Blades ovate to orbicular, base cordate; peduncle pubescent; sepals ciliate along the lower half only; petals violet; plants growing on dry loam in margins of open, hardwood and mixed forests, shaded ledges, disturbed sites - V. sororia
9b. Blades reniform to deltoid-ovate, base subtruncate to cordate; peduncle glabrous; sepals finely ciliate; petals violet-blue; plants growing on sandy or silty alluvial soils in low woods, floodplains, ravine bottoms, and creek banks - V. missouriensis

10a. Blades divided into three or five linear to subspatulate segments with mucronulate apex, middle segment equal to the lateral segments; sepals acute; petals violet; trichomes present on the spurred petal; plants growing in prairies, prairie relicts on banks of railroad tracks, and margins of fields - V. pedatifida
10b. Blades reniform and trilobed, middle lobe of trilobed blades widest, widely obovate or oblong with obtuse apex; sepals obtuse; petals violet to purple-violet; trichomes absent on the spurred petal; plants growing in margins and openings in rich, often rocky woods - V. triloba

11a. Blades undivided and unlobed (including uncleft and unlobed above base) - 12.
11b. Blades divided or both trilobed and reniform - 19.

12a. Margin type of the blade base different from the margin type of the blade above base - 13.
12b. Margin type of the blade base same as the margin type of the blade above base - 14.

13a. Blades oblong to oblong-ovate; blade base cordate to subcordate, margins of blade base sharply dentate, peduncles of cleistogamous flowers prostrate; seeds moderate brown; plants growing on gravelly soil or coarse sand in open Quercus forests, edges of forests and forest roads - V. fimbriatula
13b. Blades lanceolate-deltoid; blade base sagittate, margins of blade base entire to coarsely crenate; peduncles of cleistogamous flowers erect; seeds deep brown or deep yellowish brown; plants growing on sandy soil or sandy-loam in open grounds, mesic sand prairies, and open sites in forests - V. sagittata

14a. Peduncles of cleistogamous flowers prostrate; capsules spotted with red-purple - 15
14b. Peduncles of cleistogamous flowers erect or ascending; capsules green or yellow-green - 18

15a. Seeds orange-yellow to strong yellowish brown - 16
15b. Seeds dark grayish brown or dark yellowish brown - 17

16a. Blades deltoid, margins crenate-serrate with uneven serrations, base deeply cordate to auriculate, apex bluntly attenuate; capsule length/width ratio 2-2.2, sparsely spotted and dotted with red-purple on a yellow-green background, glabrous; sepal length/capsule length ratio 0.2-0.4; seeds dark orange-yellow to strong yellowish brown; plants growing on sandy or silty alluvial soils in low woods, floodplains, ravine bottoms, and creek banks - V. missouriensis
16b. Blades narrowly ovate, margins crenate, base cordate with a deep sinus, apex acute; capsule length/width ratio 1.5-1.6, densely spotted and dotted with red-purple on a yellow-green background, often pubescent; sepal length/capsule length ratio 0.4-0.5; seeds moderate orange-yellow; plants growing on rich loam in low shady borders of lakes and streams and low woods, wet thickets and meadows - V. affinis

17a. Blades ovate to orbicular; capsule length/width ratio 1.6-1.8; seeds dark grayish brown, 1.9-2.4 mm long, 1.2-1.5 mm wide; plants growing on dry loam in margins of open, hardwood and mixed forests, shaded ledges, disturbed sites - V. sororia
17b. Blades broadly ovate to cordate; capsule length/width ratio 1.4-1.6; seeds dark yellowish brown, 1.6-2.1 mm long, 0.9-1.0 mm wide; plants growing on loam, often mixed with coniferous litter, in openings in coniferous woods, open groves of Thuja occidentalis, open mixed woods - V. septentrionalis

18a. Blades light-green on the adaxial surface; auricles on cleistogamous flowers and capsules 3-5 mm long, ciliate; capsule length/width ratio 2.2-2.5; seeds nearly blackish red, occasionally dark brown, often with flat seed coat on one side; plants growing in swamps, bogs, wet meadows, rock crevices in slow streams, often submerged in soaked muck, dark humus or Sphagnum mats - V. cucullata
18b. Blades light gray-green on the adaxial surface; auricles on cleistogamous flowers and capsules 0.5-1 mm long, eciliate; capsule length/width ratio 1.2-1.5; seeds dark yellowish brown to dark brown, without flat seed coat on one side; plants growing on calcareous loam in cool, shaded wet banks of slow streams, rivers, and lakes or wet soil pockets of protected rock crevices - V. nephrophylla

19a. Plants homophyllous - bearing only divided blades, division up to five times, blade segments linear to subspatulate; peduncles of cleistogamous flowers erect; capsule yellow-green; seed color close to strong yellowish brown; plants growing in prairies, prairie relicts on banks of railroad tracks, and margins of fields - V. pedatifida
19b. Plants heterophyllous - bearing trilobed and unlobed, reniform blades; peduncles of cleistogamous flowers prostrate; capsule blotched and spotted with red-purple on a yellow-green to green background; seeds color dark orange yellow; plants growing in margins and openings in rich, often rocky woods - V. triloba

START THIS KEY


Please email keystonature@fieldmuseum.org with questions or concerns.
This page was last modified on: Thu, 27 Oct 2011 22:01:32 -0500.