[2.12] Viola sect. Nosphinium

Viola sect. Nosphinium W. Becker in Engler, Nat. Pflanzenfam., ed. 2 [Engler & Prantl], 21: 374. 1925 ≡ Viola subg. Nosphinium (W. Becker) Espeut in Botanica Pacifica 9(1): 34. 2020.—Lectotype (Espeut 2020 [61], page 34): Viola chamissoniana Ging.

Description.—Perennial herbs (subshrubs or treelets in most species of subsect. Nosphinium). Axes in some species morphologically differentiated into a perennating stem and annual aerial stems (subsect. Langsdorffianae, modified in subsect. Nosphinium) or stolons (some species of subsect. Mexicanae). Perennating stem usually a rhizome, deep or shallow, vertical or horizontal, terminating in an apical rosette. Stipules membranous or partially herbaceous, free (basally or strongly adnate in a few species of subsect. Mexicanae), glandular-fimbriate to glandular-laciniate. Lamina various, long-petiolate. Corolla violet (white in a few species of subsect. Mexicanae and subsect. Nosphinium), throat white. Calycine appendages short and rounded or elongate, quadrate and often dentate, often elongated somewhat in cleistogamous fruit. Petals large, lateral petals glabrous or sparsely to densely bearded within (spurred petal bearded in some species of subsect. Borealiamericanae). Spur thick, as long as tall (sometimes nearly twice as long as tall in V. langsdorffii). Style cylindrical with slight subapical swelling (subsect. Langsdorffianae), or clavate with apex flanked by a dorsolateral sharp edge or protruding thickened apically oriented or spreading rim, stigma on a pronounced rostellum. Cleistogamous flowers produced, mostly seasonal (cleistogamy absent in subsect. Pedatae and in most species of subsect. Nosphinium). Allodecaploid with one 2x genome from sect. Chamaemelanium, one or more 4x genomes from sect. Plagiostigma, and one 4x genome from sect. Viola. ITS sequence of MELVIO (sect. Viola) type. Inferred secondary base chromosome number [x’ = 28].

Diagnostic characters.—Rosulate habit (rarely stoloniferous or with aerial stems) AND rhizome thick AND stipules free (rarely adnate) AND corolla violet (rarely white) AND petals large AND spur thick and short AND style clavate with dorsolateral edge or thickened rim and pronounced rostellum (rarely with merely a weak dorsolateral swelling) AND allodecaploid with one 2x genome from sect. Chamaemelanium, one or more 4x genomes from sect. Plagiostigma, and one 4x genome from sect. Viola.

Ploidy and accepted chromosome counts.—10x, 14x, 18x, ~22x; 2n = c. 44, 54, c. 76, 80, c. 80, c. 85, c. 86, c. 96, 102, c. 120.

Age.—Crown node 8.4 (7.5–8.8) Ma [28].

Included species.—62.

Distribution.—North America, Hawaiian Islands, Mexico and Central America, a few species in northern South America, one species in northeastern Asia

Discussion.