[2.13.2] Viola sect. Plagiostigma subsect. Bilobatae

Viola subsect. Bilobatae (W. Becker) W. Becker in Acta Horti Gothob. 2: 288. 1926 

≡ Viola [sect. Nomimium; unranked] (“Gruppe”) Bilobatae W. Becker in Beih. Bot. Centralbl., Abt. 2, 34: 226. 1917 

≡ Viola ser. Bilobatae (W. Becker) Steenis in Bull. Jard. Bot. Buitenzorg, ser. 3, 13 (1933–1936): 260. 1934 

≡ Viola sect. Bilobatae (W. Becker) Juz. in Schischk. & Bobrov, Fl. URSS 15: 439. 1949

—Lectotype (Espeut 2020 [61], page 33): Viola arcuata Blume

Description.—Rhizome perennial; bulbils absent. Lateral stems present or rarely absent: aerial stems, decumbent or erect, leaves scattered. Stipules free or adnate at base only, green and foliaceous, up to 40 mm, linear-lanceolate to ovate, obtuse to acuminate, entire, remotely denticulate or lobed. Lamina ovate-triangular to narrowly triangular or nearly hastate, base truncate to broadly cordate, often with a lunate sinus, apex more or less acute, margin crenulate. Corolla white. Sepals linear to ovate-lanceolate; appendages short (c. 0.5 mm), rounded or slightly denticulate. Lateral petals bearded or not; bottom petal shorter than the other petals (6–8 mm), apex rounded; spur short (1–2 mm) and saccate. Style at apex margined and bilobate.

Diagnostic characters.—Stipules foliaceous AND style margined and distinctly bilobate at apex.

Ploidy and accepted chromosome counts.—4x, 8x; 2n = 24, 44, 48.

Age.—Crown node age c. 4.7 Ma (Figure 6), stem node age 13.5 (12.2–14.0) Ma [28].

Included species.—8. 

Viola amurica W. Becker, > iNat

Viola caleyana G. Don,  > iNat

Viola cunninghamii Hook. f., >iNat

Viola hamiltoniana D. Don, > iNat

Viola lyallii Hook. f., >iNat

Viola merrilliana W. Becker, 

Viola raddeana Regel, 

Viola triangulifolia W. Becker >iNat

Distribution.—Eastern Asia, Malesia, Australia, New Zealand.

Discussion.—The overall morphology of sect. Plagiostigma subsect. Bilobatae is superficially similar to that of the unrelated sect. Viola subsect. Rostratae, and conspicuously so in species such as V. raddeana (Bilobatae) and V. stagnina (Rostratae), which both are adapted to floodplain habitats. Reported chromosome counts of 2n = 20 in subsect. Bilobatae (cf. [61]) are likely errors.

Photogallery