Commelina persicariifolia Redoute

Commelina persicariifolia Redouté Commelina persicariifolia Redouté (Redouté 1815: pl. 472). – Phaeosphaerion persicariifolium (Redouté) C.B.Clarke (Clarke 1881: 137). – Phaeosphaerion persicariifolium (Redouté) C.B.Clarke var. persicariifolium (Clarke 1881: 137). – Athyrocarpus persicariifolius (Redouté) Hemsl. (Hemsley 1885: 386). – Commelinopsis persicariifolia (Redouté) Pichon (Pichon 1946: 227). Commelina quitensis Benth. (Bentham 1846: 258). – Type: ECUADOR – Pichincha • Puente de Guapulo prope Quito; alt. 8000 ft.; s.dat.; fl., fr.; K. T. Hartweg 1439; lectotype: K [K000531988]!, designated by Hassemer (2018b); isolectotypes: K [K000531987]!, LD [LD1221669]!. Syn. nov. Etymology From the Latin ʻ persicarius ʼ (meaning ʻpeach treeʼ) + ʻ folia ʼ (meaning ʻleafʼ), in reference to its leaves being similar to those of the genus Persicaria Mill. (Polygonaceae), which was named after its leaves, which look similar to those of peach trees [Prunus persica (L.) Batsch, Rosaceae]. Type material Original illustration of Les Liliacées at the W. Graham Arader Gallery and later published in Redouté 1815: pl. 472; lectotype, designated here. Remarks Commelina persicariifolia was cultivated in the gardens of the Muséum dʼHistoire naturelle Paris (Redouté 1815). However, the author states not knowing where the plant was originally collected. After analysing the protologue and original illustration of C. persicariifolia Redouté, it became clear that this species does not represent a synonym of C. rufipes nor of C. obliqua as it has been widely accepted for the past 200 years or so. Redouté (1815) describes his new species as presenting cordate spathe and flowers with subequal, light blue to lilac petals, which would place this species near the C. diffusa or C. tuberosa groups. Redouté (1815) describes the inflorescences as presenting very short peduncles, which is also shown in the original illustration (Redouté 1815: pl. 472). Furthermore, the illustration shows the inflorescences being produced in an apparently terminal position. These inflorescence characters could suggest C. persicariifolia to be a member of any of the C. benghalensis, C. erecta, C. robusta, or C. tuberosa groups. The association with the C. robusta group was previously made by Hunt (1981) and Faden & Hunt (1987), but no rationale was provided. Nonetheless, all species in this group have unequal petals, which also applies to the C. benghalensis and C. erecta groups. Another peculiarity in the original illustration of C. persicariifolia is that the leaves are spirally-alternate, a very rare feature in the genus that has been greatly overlooked. This peculiar character gave us the needed information to ascertain this name’s identity and application. After analysing the type of C. quitensis, we noticed that the leaves are also spirally-alternate, which is shared with some other members of the C. tuberosa group. The very short peduncle could merely be an optical artefact of the angle illustrated by Redouté (1815: pl. 472). Furthermore, Redouté (1815) provides no measurement for the length of the peduncle, making “short” and “long” very relative terms. Regardless, the type specimens of C. quitensis present comparatively short peduncles in regard to the many species of the C. tuberosa group. Furthermore, the inflorescences are mostly leaf-opposed, but an apparently terminal inflorescence is also observed in the illustration. This feature is shared with several species of the C. tuberosa group but absent in the C. diffusa group. Of the 17 species currently recognised in the C. tuberosa group, C. quitensis is by far the best match. Both species share erect, branched and glabrous stems, spirally-alternate pseudopetiolate leaves, leaf-sheaths with setose margins, a combination of leaf-opposed and apparently terminal inflorescences with short peduncles, cordate spathe with free base, developed and exserted but generally flowerless upper cincinnus, green and opaque free sepals, light blue to lilac flowers, and the shortly-clawed medial petal. Based on the aforementioned characters, we consider C. persicariifolia and C. quitensis to be conspecific. Since C. persicariifolia has priority over C. quitensis, it is treated as the correct name for this taxon, with C. quitensis reduced to a synonym.