[2.18] Viola sect. Viola

Viola sect. Viola 

≡Viola sect. Nomimium Ging., p.p. in Mém. Soc. Phys. Genève 2(1): 28. 1823, nom. inval. (Szhenzhen Code Art. 22.2; Viola odorata L.) 

≡ Viola subg. Nomimium (Ging.) Peterm., Deutschl. Fl.: 64. 1846, nom. inval. (Szhenzhen Code Art. 22.2)

≡Viola [sect. Nomimium; unranked] §.4. Rostellatae Boiss., Fl. Orient. 1: 451. 1867, nom. inval. (Szhenzhen Code Art. 22.2; Viola odorata L.) 

≡ Viola subsect. Rostellatae (Boiss.) Rouy & Foucaud, Fl. France [Rouy & Foucaud] 3: 3. 1896, nom. inval. (Szhenzhen Code Art. 22.2). 

≡ Viola sect. Rostellatae (Boiss.) J. C. Clausen in Madroño 17: 196. 1964, nom. inval. (Shenzhen Code Art. 22.2)

≡Viola [sect. Nomimium; unranked] a. Rostellata Nyman, Consp. Fl. Eur. 1: 76. 1878, nom. inval. (Szhenzhen Code Art. 22.2; Viola odorata L.)

Description.—Perennial herbs. Axes morphologically differentiated in a perennial rhizome with lateral stems; sometimes only one type of stem produced. Rhizome creeping or vertical, branched or not, with apical rosette of leaves. Lateral stems annual aerial stems, stolons, or absent. Stipules usually free, entire, dentate, laciniate or fimbriate, sometimes large and foliaceous. Lamina reniform to rhomboid, crenulate, petiolate. Flowers scented or scentless. Corolla violet to white, with a white throat. Spur (much) longer than tall, up to 16 mm. Style clavate or rarely filiform, at apex not margined, bearded or not. Capsule trigonous and explosive or globose and non-explosive. Cleistogamous flowers usually produced; cleistogamy seasonal, rarely facultative. Allotetraploid (CHAM + MELVIO). Secondary base chromosome number x’ = 10. ITS sequence of MELVIO type.

Diagnostic characters.—Perennial herbs AND corolla with a white throat AND style clavate, unmargined AND base chromosome number x = 10.

Ploidy and accepted chromosome counts.—4x, 8x; 12x; 2n = 20, 40, 58, 60.

Age.—Crown node 11.8 (10.1–12.4) Ma [28].

Included species.—75.

Distribution.—Throughout the temperate zone of the northern hemisphere; one species in southern South America (Figure 1). Diversity centre in western Eurasia.

Discussion.—Section Viola is phylogenetically an allotetraploid CHAM + MELVIO lineage and has retained the MELVIO homoeolog for ITS (Figure 6). Karyologically it is characterised by the secondary base chromosome number x’ = 10, and morphologically by the clavate unmargined style. Section Viola is one of three species-rich segregates of Becker’s widely delimited sect. Nomimium, which comprised nearly all the temperate herbaceous, violet- or white-flowered taxa with seasonal cleistogamy. Section Viola differs from both sect. Plagiostigma and sect. Nosphinium in having the base chromosome number x = 10 and a unmargined style, sometimes bearded above.

Section Viola is phylogenetically subdivided into two morphologically well-defined groups (Figure 2), here treated as subsect. Rostratae and subsect. Viola.

Key to the subsections of sect. Viola

1a.

Capsules globose, often hairy, non-dehiscent, on decumbent peduncles. Seeds large, with conspicuous elaiosome more than half the length of the seed (myrmecochory). Lateral stems stolons or absent. Style glabrous. ..................................................................................................................................................................................... subsect. Viola

1b.

Capsule elongate, trigonous, glabrous, forcibly ejecting seeds after dehiscence, on erect peduncles at maturity. The elaiosome much less than half the length of the seed (diplochory). Lateral stems usually aerial (occasionally stolons or absent). Style bearded above or beardless. ................................................................................ subsect. Rostratae

1a.