[2.14] Viola sect. Rubellium

Viola sect. Rubellium W. Becker in Nat. Pflanzenfam., ed. 2 [Engler & Prantl], 21: 374. 1925.

—Type (Shenzhen Code Art. 10.8): Viola rubella Cav.

=Viola [unranked] § II. Tri(-Pluri-)Caules Reiche in Fl. Chile [Reiche] 1: 140. 1896, nom. inval. (Shenzhen Code Art. 21.2)

Description.—Perennial subshrubs. Axes morphologically (weakly) differentiated in a perennial monopodial aerial stem and lateral monopodial aerial elongated stems bearing flowers; lateral stems with distichous phyllotaxy in Viola portalesia. Stipules small, bract-shaped, fimbriate. Lamina oblong to lanceolate, base cuneate, margin crenate, short-petiolate. Peduncle long. Corolla violet to whitish inward with a greenish throat, or magenta to pink throughout (V. rubella). Spur short. Style clavate, at apex neither margined nor bearded, bent into a simple, ventrad rostellum, or apex rounded with the rostellum on the ventral surface. Cleistogamous flowers not produced. Diploid. Base chromosome number x = 6.

Diagnostic characters.—Subshrubs AND corolla magenta or violet AND style apex strongly bent ventrad or with stigma on ventral side AND diploid with 2n = 12.

Ploidy and accepted chromosome counts.—2x; 2n = 12 (V. rubella).

Age.—Crown node age 1.6 (0.4–2.2) Ma; stem node 26.5 (25.7–26.8) Ma [28].

Included species.—3. Violacapillaris Pers., V. portalesia Gay, V. rubella Cav.

Distribution.—Central Chile

Discussion.—Section Rubellium is phylogenetically isolated and the only subshrubby diploid lineage within subg. Viola [60]. The original delimitation was established by Becker (1925). Previously, Reiche [122,130] circumscribed the group under an invalid taxonomic rank (i.e., the unranked Tri(-Pluri-)Caules within the invalid Division Sparsifoliae). Sparre [63] included in sect. Rubellium also the herbaceous V. huidobrii, by us reclassified in sect. Viola subsect. Rostratae.