Haec species Diplycosiae urceolatae simillima, sed ab eo petiolo viridi vel viridi ex roseo 4–7 mm longo, lamina 7–7.5 cm lata, lobis calycis acutis, calyce fructus maturo lavandulo differt.

PHILIPPINES. Mindanao Island, North Cotabato Province, Barangay Ilomavis, Mount Apo Natural Park, Matingao River Watershed, road from Site C to Site H at Energy Development Corporation (EDC), 1718 m, 6°59.88498'N, 125°14.86668'E, 29 Apr 2014, D.S. Penneys 2302 (holotype: PNH!; isotypes: CAS-1196249!, CMUH-00010804!).

Terrestrial erect shrublet to 0.6 m tall with ascending-erect branchlets. Young branchlets not observed; old branchlets gray, stout (3.5–4.5 mm wide), subterete, with non-peeling epidermis, glabrous. Leaves spirally arranged, with distinct wintergreen odor when crushed (fresh leaves), ascending; petiole green or slightly flushed pink, 4–7 × 2.5–2.9 mm, grooved above, glabrous; lamina broadly obovate to subrotund, the larger 8.3–9.7 × 7–7.5 cm, 1.2–1.7 times as long as wide, coriaceous, abaxially glossy and evenly dark red-dotted over the surface, adaxially shiny and glabrous; major veins prominent abaxially, sulcate adaxially, major secondary veins originating on proximal half, 1 to 3 on each side of midvein, arching-ascending, alternate, occasionally 3 on one side and only 2 on the other; base broadly cuneate, margin entire, revolute, glabrous, apex rounded or strongly emarginate, the very tip with a thick protruding dark gland to 0.8 mm long. Inflorescences axillary or on older sections of defoliated branchlets proximal to the leaves, fasciculate, 3- to 6-flowered, often with up to 7 additional old fruiting pedicels; bracts ovate-deltoid, 1.5–2 × 1.2–1.7 mm, appressed-puberulent. Pedicels slightly dilated distally, 4–7 × 0.5–0.8 mm, muriculate with short (to 0.16 mm long) ferrugineous erect or ascending trichomes, and also pubescent with pale ferrugineous irregularly oriented straight to slightly undulate nonglandular trichomes to 0.3 mm long; bracteoles ovate-deltoid, 1–1.5 mm long, muriculate, rarely also sparsely puberulent along midvein, midvein planar to prominent, margin ciliolate with a mix of ferrugineous glandular trichomes and pale ferrugineous nonglandular trichomes. Calyx green strongly flushed deep pink, 2.2–2.7 × 3.4–3.7 mm, sparsely muriculate or glabrous; limb ca. 2 mm long; lobes broadly deltoid-ovate, 1.1–1.2 × 1.8–2 mm, margins with a mixture of ferrugineous glandular and pale ferrugineous nonglandular trichomes, the latter more prevalent distally, apex acute. Corolla 5-lobed, white slightly flushed with dull pink distally, broadly urceolate, widest at middle, ca. 4.5 × 2.9 mm, glabrous both outside and within; lobes recurved, ovate, ca. 1 × 1 mm, margins eciliolate, apices obtuse. Stamens 10, included within corolla, ca. 4.5 mm long; filaments ± S-curved, ca. 3 mm long, glabrous; anthers 1.7–1.9 mm long, thecae 1.4–1.5 mm long, echinulate, tubes parallel, 0.3–0.4 mm long, smooth, pores strongly oblique. Nectary 10-lobed; lobes emarginate. Ovary cylindric-hemispherical, ca. 1.5 × 1.5 mm. Style 2.5–3 mm long, glabrous. Immature fruit green flushed red, 5–6 × 5–6 mm, style persistent; mature fruiting calyx lavender, accrescent, fleshy.

Figure 1. 

Diplycosia platyphylla P.W.Fritsch. A Habitat B Habit C Branchlet with inflorescences D Inflorescence E Immature fruit. (D.S. Penneys 2302). Scale bars: C = 10 cm, D, E = 1 cm. Photos P.W.F.

Figure 2. 

Diplycosia platyphylla P.W.Fritsch. A Fertile branchlet B Pedicel and flower C Calyx lobe apex D Flower with calyx and corolla partly cut away to show androecium and gynoecium E Stamen, ventral view F Stamen, lateral view G Immature fruit H Fruiting pedicel. Drawing by L. Heagy from D.S. Penneys 2302 (CAS) and photographic images of the living plant.

The species is named for its notably wide leaves relative to those of most other species in the genus.

Flowering and fruiting in April.

Diplycosia platyphylla is known only from a single location on Mt. Apo, Mindanao Island, North Cotabato Province, Philippines. Several individuals were found growing in gravel on an ultramafic open sunny rockslide area in the Tropical Lower Montane Rain Forest biome at 1718 m a.s.l. with Nepenthes L., Huperzia Bernh., and Vaccinium L. on a general NW-facing 30–60% slope but in a flat microhabitat along a roadside.

Diplycosia platyphylla is known from a single population and single collection, with only several plants seen. Although the species is afforded protection by its occurrence in Mount Apo National Park, it is at risk through apparent extreme rarity. We categorize this species as Critically Endangered (CR): D.

The new species is similar to Diplycosia urceolata Stapf from Mount Kinabalu in Borneo, Sabah, Malaysia by its stout glabrous branchlets, coriaceous glabrous leaf blades with rounded apices, and 4–7 mm-long pedicels with a mixture of muriculate trichomes and pale ferrugineous nonglandular trichomes. It differs from this species most readily by its green or slightly flushed pink petioles 4–7 mm long (vs vivid red and 10–13 mm), wider leaf blades [7–7.5 cm vs (2.5–)3.5–5(–7.5) cm], acute calyx lobe apices (vs obtuse), and lavender mature fruiting calyx (vs black). It is also similar to D. sanguinolenta Sleumer from Mount Kinabalu in its large coriaceous leaf blades [9–14(–17) × 5–8(–9.5) cm for D. sanguinolenta; Sleumer 1967] and generally acute calyx lobes, but is easily distinguished by a petiole 4–7 mm long (vs 12–15 mm) and a white corolla ca. 4.5 mm long (vs bright red and 13–15 mm long), among other characters. The new species would key to couplet 3 of the key to the Philippine Diplycosia in Argent (2013). The two leads at that point in the key identify the varieties of D. luzonica (A.Gray) Merrill, i.e., D. l. var. calelanensis (Elmer) Sleumer and D. l. var. merrittii (Merrill) Sleumer, distinguished by “Leaves broadly pointed to rounded with the terminal gland forming a short mucronate point the largest leaves up to 5 cm long” vs “Leaves acuminate, with a narrowly acute apex, the largest leaves more than 6 cm long,” respectively. Because the new species possesses leaves that are rounded (or strongly emarginate) at the apex but are 8.3–9.7 cm long (the larger ones), the new species does not match either of these leads. Thus, it can be distinguished from all other Philippine Diplycosia by the combination of glabrous branchlets and (larger) leaf blades 8.3–9.7 mm long with an apex that is rounded or strongly emarginate, and with a prominent terminal gland.