Pteroceras viridiflorum (Thwaites) Holttum (1960: 272)

Priyadarshana, Tharaka S., Atthanagoda, Anusha G., Wijewardhane, Ishara H., Siriweera, Kawshalya S., Aberathna, Nimantha & Kumar, Pankaj, 2019, Pteroceras dalaputtuwa (Orchidaceae: Epidendroideae: Vandeae: Aeridinae), a new species from Sri Lanka and re-collection of Pteroceras viridiflorum after 150 years, Phytotaxa 399 (1), pp. 65-76 : 70-71

Pteroceras viridiflorum (Thwaites) Holttum (1960: 272) [ Figs. 5–7 ]

Aerides viridiflorum Thwaites (1864: 430) Sarcochilus viridiflorus (Thwaites) Hooker (1890: 38) TYPE: — SRI LANKA. Central Province, Gardner s.n., (C.P.3385A) (PDA!: Lectotype designated here); SRI LANKA. Central Province,

Gardner s.n., (C.P.3385B) (PDA!: Paralectotype designated here); SRI LANKA. Moray Estate, Maskeliya, Nuwara Eliya District ,

Central Province, 2 August 2016, Atthanagoda AKAG 02 (PDA!: Epitype designated here)

Description: Epiphytic, succulent herbs. Stems short, non-pseudobulbous, bearing stout, flexuous and long roots at the base. Leaves 3 to 6, falcately oblong or ovate, 5.0– 7.5 cm long × 1.5–2.0 cm wide, distichous, sessile, rather fleshy, mid-rib prominent, unequally bilobed at apex. Inflorescence racemose, glabrous, green, axillary from base of the stem, pendulous, 1.5–3.0 cm long, bearing 3–5 flowers (often only 3 flowers). Flowers bright pale-green with a white lip, ca. 0.9–1.2 cm across; bracts minute, broadly ovate, obtuse, bright pale-green, 0.28 cm long, 0.24 cm wide; pedicel green-yellow, wrinkled, terete, pedicel with ovary 0.28 cm long; sepals and petals dissimilar, petals smaller than sepals; dorsal sepal ovate to broadly ovate, with rounded apex, 0.6 cm long × 0.4 cm wide, 5-veined; lateral sepal ovate, obtuse, adnate to the foot of the column with a broad base, reddish maroon tint near the base, 5-veined, 0.7 cm long × 0.55 cm wide; petals linear-oblong, obtuse, 1-veined, 0.5 cm long × 0.3 cm wide; lip adnate to a sort (0.5 mm long) column foot, 3-lobed, 0.6 cm long × 0.3 cm wide; side-lobes small, oblong, blunt and erect, reddish-maroon on inner surface (sometimes pure white— Fig. 7 ), 0.5 cm long × 0.2 cm wide; mid-lobe, clawed-like, white with reddish-maroon markings between the side-lobes; labellum with spur, ending in a semilunar limb with round and tapering apex, fleshy, white, hollowed, inner wall with fine hairs; column short, 0.28 cm long, pale green; anther 2-loculed, 0.18 cm long × 0.10 cm wide; pollinia 4, pale-yellow, cleft, globular shape, with stripe, 0.10 cm long × 0.09 cm wide; capsule cylindrical, elongated, often with a short beak, unripe banana-like, 3.7–4.0 cm long.

Flowering: —August to December

Habitat and Ecology: —Epiphytic plants growing on lichen and moss covered tree trunks; well attached to the bark, under almost 90% shade. All our observations are from the following locations in Sri Lanka; Dehenakanda-Adam’s peak (Samanala Nature Reserve) foot path in Rajamale, Hatton-Adam’s peak (Samanala Nature Reserve) foot path and Moray Estate, Maskeliya.

Specimen Examined: — SRI LANKA. s.coll., C. P.4016 ( PDA!) ; 19 November. 1923, Stedman s.n. ( PDA!) ; Moray Estate, Maskeliya, Nuwara Eliya District , Central Province, 2 August 2016, Atthanagoda AKAG 02 ( PDA!) .

Taxonomic Notes: Thwaites (1864), while describing Aerides viridiflorum , studied more than one illustration from Sri Lanka, as he mentioned, “described from coloured drawings in his collection” (note the plural ‘drawings’). His description was based on two drawings made by A.D. Alwis. Those drawings were based on Gardner’s specimens collected from the Central Province of Sri Lanka, both of which were labelled as “ C.P.3385 ”. Hooker (1890) noted in his description, “I have seen only one small specimen and a coloured drawing”, referring to the specimen C.P.4016 collected by Trimen and one of the illustrations of C.P.3385 based on Gardner’s specimens from the Central Province of Sri Lanka. Trimen (1898) also referred to Gardner’s specimens used for C.P.3385 drawings collected from the Central Province of Sri Lanka, and he mentioned another specimen of Nevill, collected from Dunsinane Estate, Great Western Mountain, Sri Lanka. He also added that he did not see Gardner’s specimens C.P.3385 and C.P.4016 has no locality mentioned. Later, Jayaweera (1981) noted in his description, “very little is known of this species from Ceylon ( Sri Lanka) except from drawings”. However, among the materials that Jayaweera (1981) studied, he mentioned two illustrations under C.P.3385 and three specimens: C.P.3385 (PDA), C.P.4016 (PDA, K) and Stedman s.n. (PDA). Jayaweera (1981) also reproduced a black & white illustration of C.P.3385 for his publication (see Fig. 85, page number 191).

After consulting PDA we found two illustrations (C.P.3385 —two drawings) and two specimens ( Sri Lanka, s.coll., C.P.4016 and Sri Lanka, 19 Nov. 1923, Stedman s.n.). It is not possible for the authors to reproduce digital images of those two illustrations (C.P.3385) due to copyright issues, hence a suffix ‘A’ is added to C.P.3385 as C.P.3385A (the same illustration reproduced by Jayaweera (1981: page 191, fig. 85) and to the other one a suffix ‘B’ is added as C.P.3385B. We designate C.P.3385A as the lectotype and C.P.3385B as the paralectotype. At the same time, we realised a good specimen is needed to understand the characters in detail. Hence, we designate a freshly collected specimen, ‘ Atthanagoda AKAG 02 ’ __ deposited at PDA as the epitype. Designation of the epitype is based on Article 9 of International Code of Nomenclature ( McNeill et al. 2012).

Jayaweera (1981) wrongly linked P. viridiflorum to an Indian species, Loxoma viridiflora (Dalz.) Pradhan [now Smithsonia viridiflora (Dalz.) Saldanha ], which is clearly a different taxon and endemic to India ( Pedersen 1993; Fernando & Ormerod 2008). Consequently, the description of Hooker (1890) and Jayaweera (1981) are incomplete, and these two descriptions have some mismatching characteristics too. Pedersen (1993) also noted that the taxonomic affinity of P. viridiflorum is unclear and recognised it as an endemic species to Sri Lanka. Moreover, during a recent conversation, after looking at the current description and colour plates prepared from fresh and preserved specimens, Dr. Pedersen is sure about the identity of this species as well as its placement under the genus Pteroceras (H.AE.Pedersen, pers. comm.). Hence, a detailed description is provided here for P. viridiflorum based on the live and preserved specimens recently collected by the authors from Sri Lanka.

Conservation Status: — P. viridiflorum is endemic to Sri Lanka and it was assessed as a CR(PE) species in the National Conservation Statuses (NCS) of the National IUCN Red List 2012, Sri Lanka (MOE 2012). However, this new finding reveals that NCS of P. viridiflorum must be downgraded to Critically Endangered [CR(D)] based on the fact that the total number of mature individuals is around 20 (<50).

Figures

FIGURE 5. Pteroceras viridiflorum (Thwaites) Holttum, A. Plant (in-situ). B. Close-up of plant. C. Close-up of flowers. Photo credit to Anusha G. Atthanagoda.

FIGURE 6. Pteroceras viridiflorum (Thwaites) Holttum (alcoholic specimen), A. Close-up of flower, B. Flower–front view of a spreadout specimen. C-J. Dissected flower; C. Bract, D. Dorsal sepal, E. Petal, F. Lateral sepal, G. Vertical dissection of hollowed spur-like showing fine hairs on the inner wall, H. Lip with spur and column, I. Side-view of labellum showing foot, column and spur, J. Column showing stigma and pollinarium inside the anther cap, K. Operculum, L. Pollinarium. Photo credit to Tharaka S. Priyadarshana.

FIGURE 7. Pteroceras viridiflorum (Thwaites) Holttum, A white colour variant (see the white lip). Photo credit to Anusha G. Atthanagoda.