[2.12.2] Viola sect. Nosphinium subsect. Clausenianae 

Viola subsect. Clausenianae H. E. Ballard, subsect. nov.

—Type: Viola clauseniana M. S. Baker

Description.—Perennial herbs. Axes not morphologically differentiated; stem a perennial rhizome terminating in an apical rosette. Stipules narrow, adnate in lowest 1/3. Laminas undivided. Calycine appendages short and truncate to rounded. Petals violet, beardless. Style clavate, the apex triangular from above, the pronounced thickened dorsolateral rim protruding apically as a broadly truncate or weakly emarginate margin continuing down to the rostellum, the rostellum oriented apically or incurved. Cleistogamous flowers produced, seasonal.

Diagnostic characters.—Habit strictly rosulate AND stipules basally adnate AND petals violet AND all petals beardless AND style with apically protruding broadly truncate dorsolateral rim and forward-pointing to incurved rostellum AND cleistogamy present.

Ploidy and accepted chromosome counts.—10x; 2n = c. 44 (needs confirmation).

Age.—Crown node not applicable (monotypic subsection), stem node age 5.0–11.5 Ma [45].

Included species.—1. 

Viola clauseniana M. S. Baker

Distribution.—USA (Utah).

Discussion.—A monotypic subsection for the anomalous Utah endemic Viola clauseniana. Phylogenetic analyses place it firmly among other Nosphinium groups but indicate only ambiguous placement otherwise. Genetically it appears to retain the initial allodecaploid constitution of the ancestor of the section [45], which puts into question the count of n = c. 22 reported by Clausen [59] from the type locality; we would rather expect n = 27 as in the subsections Borealiamericanae and Pedatae. While most similar morphologically to the Borealiamericanae, the absence of petal beards, basally adnate stipules, and style with dorsally protruding and very thickened dorsolateral rim and a forward-pointing to incurved rostellum delimit it uniquely in the section. T.M. has observed unusual morphology in the cleistogamous flowers. The species is known from a single area, Zion National Park, and occurs in isolated “hanging gardens”, seasonally moist to wet cliff ledges.