Climbing aerial stem-parasitic shrubs ca. 30 cm in height; epicortical roots present, terete, glabrous, 10 cm long, stout at base, 0.8 cm becoming slender, 0.5 towards the apex, haustoria at irregular intervals, appressed against the stem of the host tree. Stems with internodes somewhat flat on younger twigs, becoming terete, 3.8–5.9 × 0.2–0.7 cm, smooth when bearing young leaves, coarsely and irregularly ridged when older, light brown to greyish-white; nodes dilated on matured stems. Leaves opposite; adaxial surface dark green and glossy, abaxial surface pale and dull, glabrous, concave, lanceolate to broadly ovate, 6.3–9.6 × 3.1–5.7 cm; margin entire; apex acute to attenuate; base cuneate, decurrent towards a channelled petiole, especially in young leaves; petioles terete, 3.4–7.8 × 2.3–2.6 mm, greyish-white on older branches, light green and almost sessile on young twigs, 2.2–3.6 × 1.2–1.8 mm; veins with mid-rib rarely pale green at base on adaxial surface, raised only on the abaxial surface, secondary venation pinnate and obscure on both sides. Inflorescences absence of involucre of decussate scales, axillary on leafless nodes; short, unbranched raceme with 5–7 opposite pairs of triads with flowers that are sessile 0.4–0.9 × 0.9–1.2 mm, bract at the base of the inflorescence absent, tomentose all throughout, except for the inner lobes of bracteoles and limb, stamen and pistil; thyrse 16.2–35 mm long, 2.1–2.6 mm wide at base, 1.3–1.8 mm wide towards the apex, terete; inflorescence internodes 1.9–4.9 × 0.5–1.3 mm; peduncle of triads terete 5.2–8.3 ×1.0–1.3 mm, secund; floral bracteoles partially fused forming a cup, 4.0–4.1 × 3.6–3.7 mm, united below the middle, cucullate, lobes of bracteoles partly overlapping at base, margin tomentose, apex obtuse, tomentose outside, glabrous inside, enclosing the ovary; ovary white, widely obovate, 2.8–2.9 × 1.4–1.5 mm; calyculus narrowly cylindrical, 0.8–1.1 × 1.3–1.2 mm, limb erect, cupular, irregularly lobed, apex acute to aristate, glabrous inside. Flowers 6-merous with corolla bud of variable colours, red or red orange at base, green at apex; mature buds usually basally red, green at tip, 26.1–29.5 × 2.3–2.5 mm long, clavate, length of corolla tube at anthesis 2.1–3.4 × 1.7–2.1 mm, becoming constricted, 2.3–3.8 × 1–1.2 mm and inflated, 3.7–3.9 × 1.7–2.4 mm, tubular and obtuse or rounded at tip, tomentose; petal lobes 11.3–15.8 mm long, broad at base 1.2–1.4 mm, middle part 0.6–0.8 mm, near apex 0.5–1 mm, coherent in the second inflated part 9–11 mm in height from base, recurved petal lobe 6.4–6.9 mm, acute to rounded at apex; stamens 25.3–27.8 × 0.2–0.3 mm; anthers 2.9–3.6 mm long, basifixed, more or less arranged at the same level, acuminate at apex, longer than the free part of the filament; disc 0.6 × 0.5 mm wide; style 28.6–29.1 × 0.3–0.4 mm long; stigma 0.27–0.29 × 0.2–0.3 mm, circular to elliptic. Fruit ovoid, 5.7–6.7 × 4.2–4.4 mm, ripening yellow-green, calyculus persistent; viscin disc 1.6–2.1 mm thick. Seeds 4.2–4.4 × 1.7–1.8 mm, white.

Decaisnina tomentosa (Fig. 1) is similar to D. confertiflora (Merr.) Barlow with respect to the presence of shortly and densely off-white tomentose inflorescence and 6-merous flowers. However, the new species differs by its rounded ste, (vs. stem internode distinctly angular), cuneat leaf base (vs. truncate or slightly cordate at the leaf base) and corolla that is distinctly inflated teice (vs. slightly inflated at the base). Also, the new species has a longer corolla measuring 27.9–29.2 mm (vs. 16–20 mm). Highly distinct flowers that are subtended with a tomentose cup formed by the fusion of the bracteoles with slightly cucullate lobes and glabrous inside which almost or entirely cover the ovary of individual flowers, and corolla tomentose, double inflated at base and middle. We consider that the combination of these and other characters presented in Table 1 are significant for the recognition of this new species.

Figure 1.  

Decaisnina tomentosa M.D.Angeles, Tandang, Carab.-Ort., & Buot. A Inflorescence with distal flowers in buds and proximal flowers at anthesis. B Inflorescence with flower buds. C Inflorescence in a secund raceme showing the tomentose rachis and bracts. D Close-up of bracts and bracteoles showing its tomentose nature. Note the tomentose indument covering all structures. E Twig with opposite leaves. Note the shiny surface of leaves with obscure venation. F Epicortical runner (right side) appressed against the stem of its host. Arrow points to a secondary haustorial connection. Photo credits: Marjorie delos Angeles.

The specific epithet “tomentosa” refers to the short soft indument densely covering the inflorescence of the new species.

This new species is known only from the type locality at the SINP in Paranas, Samar Island. The SINP is a protected area under Proclamation No. 442. 2003, pursuant the National Integrated Protected Areas System Act of 1992 (Republic Act No. 7586).

Regarding interactions with potential pollinators and seed dispersers, no floral visitors or fruit consumers were observed during our visit to the site. Given the morphological features of flowers and fruits, it is probable that they are pollinated and dispersed by birds. Systematic field observations and experimental studies are needed to assess pollinators and effective seed dispersers and to document interactions with other organisms.

During the first field survey in June 2021, we observed a tree of Baccaurea philippinensis Merr. (1915: 275) (Phyllanthaceae) parasitised by five individuals of D. tomentosa. Searches for additional individuals in the area were unfruitful. Two additional explorations to the SINP in September and October 2021 failed to locate more individuals. Since D. tomentosa is only known from five individuals on a single tree, we believe that the species is vulnerable to extinction. However, we need information from additional surveys to identify more individuals and perform quantitative assessments on its demographic profile, current distribution, host range and potential threats. Therefore, we consider that the species should be listed as Data Deficient (DD) (IUCN Standards and Petitions Subcommittee 2019) until more field assessments are conducted to ascertain its actual conservation status.

Decaisnina tomentosa has been observed bearing flowers and fruits in the month of June.

Decaisnina tomentosa resembles the widespread species complex D. sumbawensis (Tiegh.) Barlow (1997: 304) due to morphological resemblances in the colour of the mature corolla (basally red and apically green), but the former can be separated from the latter by the presence of densely covered short soft hairs on the inflorescence (tomentose vs. puberulent).