Viola pratincola Greene
Common names:
None.
Synonyms:
Viola pratincola Greene, Pittonia 4: 64. 1899. Type: U.S.A. Minnesota. Windom, 1 Jul 1898, E. L. Greene s.n. (incorrectly designated as holotype by Landon McKinney, Sida, Bot. Misc. 7: 36. 1992; corrected to lectotype by Ballard et al. 2020. Journal of the Botanical Research Institute of Texas 14(2): 225): NDG32745 (n.v.); isolectotype: NDG32746 (n.v.); both internet images).
Description:
Acaulescent rosulate perennials from thick rhizome, ≤ 15 cm tall; foliage, peduncles and calyces green, strictly glabrous; stipules free, irregularly glandular-fimbriate; largest leaves spreading to ascending, leaf blades undivided, largest ≤ ** × ** mm, in chasmogamous flower slightly longer than to as broad as long, narrowly ovate to ovate-deltate, base cordate, apex acute or subacuminate, broadening in fruit to broadly ovate-deltate to reniform, base shallowly cordate to cordate, apex commonly abruptly acute, margins uniformly crenate-serrate to the apex, eciliate; chasmogamous peduncle held among the leaves; chasmogamous flower ≤ ** mm; calyx glabrous, eciliate; lowest sepals ovate-lanceolate, apex acute to sharply acute from near the base; auricles short and truncate, weakly elongating in fruit to 1.5–2 mm; corolla blue to purple, throat white; spur short-globose; lateral petals densely bearded with filiform hairs, spurred petal sparsely bearded; all petals broadly rounded at apex; cleistogamous flowers produced after chasmogamous, on ascending to erect peduncle; capsule **–** mm, green drying to tan, unspotted, glabrous; seeds **–** × 1.0–1.3 mm, **.
Similar species:
This species would most likely be confused with other species having the foliage glabrous, leaf blades nearly as broad as to broader than long and acute at apex, and cleistogamous capsules unspotted on ascending peduncles. In chasmogamous flower it differs from Viola communis, V. domestica, V. cucullata, V. missouriensis, Viola sororia [glabrous variant] and Viola sororia [hirsutuloides variant] in its sparsely bearded spurred petal; additionally from Viola communis in its dull narrowly ovate to ovate-deltate leaf blades with acute apex and more prominently serrate margins, and ovate-lanceolate sepals acuminate from near the base; from V. cucullata in its uniformly violet to purple corolla lacking a contrasting eyespot, short truncate auricles, and long lateral petal beards; from V. domestica in its smaller stature, ovate-lanceolate acuminate sepals, and common occupation of wild habitats; from V. missouriensis in its leaf blades with uniformly serrate margins to the apex, and eciliate ovate-lanceolate acuminate sepals; and from Viola sororia [glabrous variant] and Viola sororia [hirsutuloides variant] in its ovate-lanceolate acuminate sepals. In chasmogamous flower it also differs from V. nephrophylla in its narrowly ovate to ovate-deltate leaf blades with acute apex, ovate-lanceolate acuminate sepals, and sparsely bearded spurred petal; and from V. retusa in its broader less sharply acute leaf blades, and broader sepals. In cleistogamous fruit it can be distinguished from V. missouriensis, Viola sororia [glabrous variant] and Viola sororia [hirsutuloides variant] by its unspotted cleistogamous capsule on an ascending to erect peduncle, and spotted seeds; from V. communis by its more prominently acute and serrate leaf blades, and ovate-lanceolate acuminate sepals; from V. cucullata by its shorter cleistogamous peduncle, broader sepals less than 1/2 the length of the capsule, auricles weakly elongating, and spotted seeds; from V. domestica by its taller cleistogamous peduncle, ovate-lanceolate acuminate sepals, and more densely spotted seeds; from V. nephrophylla by the ascending to erect cleistogamous peduncle, ovate-lanceolate acuminate sepals, and spotted seeds; and from V. retusa by its broader sepals and smaller seeds.
Ecology:
Wet prairies bordering streams and rivers, less often streambanks and swampy woodlands, often invading anthropogenic sites such as low-lying lawns and railroad rights-of-way.
Distribution:
s. WI to MN, ND and se. MT, south to AR, TX and c. NM.
Rarity:
None.
Phenology:
Chasmogamous flower April–May, chasmogamous fruit April–July, cleistogamous fruit May–October.
Affinities:
This species belongs to the Acaulescent Blue Violet lineage, sect. Nosphinium W.Becker, subsect. Boreali-Americanae (W.Becker) Gil-ad, in the Cucullata species group.
Hybrids:
None.
Comments:
Greene wrote in his protologue "I collected this plant in its summer condition, on the first of July, 1898, in a low meadow of natural vegetation (the land never having been ploughed) near the banks of the Des Moines River, at Windom, Minnesota. It was growing in great abundance in the rich black prairie soil among grasses and lilies (Lilium umbellatum). Copious living specimens of the plant in full vernal flower were sent me this season, from the same spot, by my niece, Miss Nellie C. Greene, so that I have now all needful data from which to determine its rank." The protologue describes one quite specific collection, but it makes no reference to a single sheet and does not mention a herbarium. The JSTOR Global Plants database has three NDG sheets, all with identical label information and no indication by Greene on any as to type status. Sheet NDG32749 is morphologically different from the other sheets in multiple traits that do not fully match the description, and this sheet should be excluded from consideration. There is no justification for why McKinney or Gil-ad arbitrarily chose NDG32745 to be the holotype. McKinney was first to designate sheet NDG32745, and his designation was corrected to lectotype by Ballard et al. (2020).
This species was noted only in passing as a name by Brainerd (1921) under his broadly defined and heterogeneous Viola papilionacea, and didn't consider it worth formal distinction. Based on his annotated collections at VT and elsewhere and his literature, however, he saw very few specimens and evidently did not cultivate it in his garden. Other taxonomists have batted Greene's name between Viola nephrophylla and Viola sororia as a synonym. Russell initially called plants in Iowa and Minnesota V. papilionacea (Russell 1953, 1959), but he later applied the name V. pratincola to those and other violets in the eastern Great Plains and western Midwest (Russell 1965). It was recently successfully delimited from other members of the Cucullata and Sororia species groups and placed in the former, due to its glabrous foliage, eciliate sepals, and unspotted cleiostogamous capsule on ascending peduncle. Numerous herbarium specimens and images express very uniform morphology, with many populations represented over several states; a living population in southern Wisconsin was also inspected. This species of wet prairies and open moist sites, especially near streams and rivers, often also invades anthropogenically disturbed sites such as low-lying lawns and railroad rights-of-way (like many other species of floodplains). It appears (based on occasional mixed collections) to occasionally grow in local sympatry with V. nephrophylla and less often with V. retusa. Viola communis, this species and V. retusa form a crude "transitional" series in which the shape of leaf blades and sepals change from orbicular to reniform-deltate obtuse to rounded leaf blades, and ovate-triangular sepals acuminate from the middle in V. communis; to narrowly ovate to ovate-deltate leaf blades, and lanceolate sepals acuminate or slightly convexly tapering from the base in V. pratincola; to narrowly ovate-triangular to triangular-deltate leaf blades, and linear-lanceolate sepals acuminate from the base. Distributions and habitats also show an apparent transition, with V. communis in floodplain-related niches of the eastern Midwest, V. pratincola in wet prairies beside streams and rivers and in other moist to wet open sites of the western Midwest and Great Plains, and finally V. retusa in sand and gravel alluvium along streams and rivers almost exclusively in the Great Plains.
Literature Cited:
Ballard Jr., H. E., R. N. Burwell, and S. L. Lockhart. 2020. Violaceae: Typifications and clarifications of names. In Weakley, A. S., D. B. Poindexter, H. C. Medford, B. A. Sorrie, C. A. McCormick, E. L. Bridges, S. L. Orzell, K. A. Bradley, H. E. Ballard, Jr., R. N. Burwell, S. L. Lockhart, and A. R. Franck. Studies in the vascular flora of the southeastern United States. VI. Journal of the Botanical Research Institute of Texas 14(2): 217-229.
Brainerd, E. 1913d. Viola. In Britton, N. L. and A. Brown, An illustrated flora of the northern United States, Canada and the British possessions. C. Scribner's sons, New York, NY, 545-563.
Brainerd, E. 1921b. Violets of North America. Vermont Agricultural Experiment Station Bulletin 224: 1-172.
Russell, N. H. 1959. The violets of Minnesota. Proceedings of the Minnesota Academy of Science 25/26: 126-191.
Russell, N. H. 1965. Violets (Viola) of the central and eastern United States: An introductory survey. Sida 2: 1-113.
Chasmogamous flowering habit from herbarium specimen: MO, Grain Valley, 7 May 1899, B. F. Bush 20 (NY04298603)
Cleistogamous fruiting habit from herbarium specimen: MO, Courtney, 5 Jun 1917, B. F. Bush 7993A (NY05376172)
Chasmogamous flower profile view from herbarium specimen: OK, Near Alva, 27 Apr 1913, G. W. Stevens 214 (MO782931)
Cleistogamous fruit from herbarium specimen: MO, Courtney, 5 Jun 1917, B. F. Bush 7993A (NY05376172)
Seeds from herbarium specimen: **
Map by Biota of North America Program