Diagnosis
Rafflesia balatociana is distinguished from closely related species by a combination of characters: bilobed outermost bract (entire in R. aurantia, R. banaoana and R. consueloae ), diaphragm discolorous from perigone lobes (concolorous in R. aurantia andR. banaoana ), a weakly dome-shaped disk (shallowly depressed centrally in R. aurantia , conspicuously dome-shaped in R. banaoana ), a dark red, leathery and distally ‘pockmarked’ (indented) upper disk surface (creamy-white to pale pink, covered with brown acicular hairs throughout in R. consuelaoe , ivory to brownish yellow in R. banaoana ), a doubly-dentate disk rim with bristles (vs. crispate in R. consueloae and R. aurantia , with minute brown hairs in R. banaoana ), a long strap-shaped lacuna on the annulus interior (contracted and blunt in R. aurantia andR. consueloae , long and basally-expanded in R. banaoana ), and an annulus exterior without a basal ridge (basal ridge prominent inR. banaoana ).
Endophytic holoparasite (devoid of a vegetative body).Mature bud 10–15 cm diameter. Cupule c. 2.5–3 cm high, 5–6 cm wide. Bracts dark brown to black, in a set of 5 imbricate whorls, 5 bracts per layer, outermost smallest, c. 2–3 cm long by 4.5 cm wide, innermost bilobed about 2 cm deep, largest, c. 9–10 cm by 8–9 cm. Flowers 25–35 cm diameter when fully expanded, 5–6 cm high. Perigone tube slanted, 5–7 cm long.Perigone lobes 5, 8–10 cm by 10 cm, 3-6 mm thick, ochre when young, reddish-brown when mature, apically recurved, broadly orbicular, basally valvate, with margins darker in color, entire, covered with conspicuous, highly embossed, small, round, elongated, sharply-edged warts, white in color, denser near the base. Diaphragm 16–18 cm diameter, 3–6 cm wide from aperture rim to base of perigone lobe, 5–9 mm thick, background discolorous, darker from the perigone, outer surface with highly embossed sharply-edged and fence-like warts, 1-2 mm high. Diaphragm Aperture 9-10 cm diameter, margin entire, white becoming concolorous with the diaphragm. Windows absent.Ramenta reddish brown, simple filiform, 2–5 mm, longer on the lower perigone tube, simple and filiform, sometimes bi-lobed, shorter on the lower surface of the diaphragm; ramenta confluent at the base, multi–lobed above. Disk 7-8 cm diameter, 1–1.5 cm thick, pale pink when young, dark red when mature, centrally dome–shaped, rim extended horizontally, margin darker in color, doubly-toothed with bristles, the upper surface smooth, shiny and leathery, ‘pockmarked’ at the distal portion, centrally with conspicuous processes about 0.5–1 cm, the undersurface white in the middle portion near the neck of the column, brownish yellow to reddish brown in the outer zone, with minute white hairs. Processes 10–15, concolorous with disk, apex with a few bristles, those of the female flower generally shorter, 5–6 cm, polymorphic, conical on the outer zone, lobed and flattened on the inner zone; those of the male flower longer, conical, pointed apically.Male flower generally larger (to 35 cm), without vestigial ovary, anthers 17–18, 3–5 mm diameter, globose, attached to a brown sub-structure about 5–8 mm wide, immersed in anther sulci 7–8 mm long and 5–8 mm wide; neck of the column 7–8 mm height, 4-4.5 cm diameter; lamella 18–20, 0.3–1 cm long from the neck margin,lacuna (or grooves between the lamella on annulus interior) 1.2–1.8 cm long and 0.3–1 cm wide, glabrous; interior annulus structure similar in size from the disk, 7–8 cm diameter, surface with small bristles, about 3 mm, reddish–brown becoming darker towards the margin, curving upward, with minute hairs; exterior annulus structure 1–2 cm from the edge of the interior annulus structure, concolorous with the disk’s upper surface, glabrous, devoid of ramenta.Female flower smaller (c. 25 cm), with vestigial white anthers in narrow grooves along the disk’s undersurface; neck of the column 7–8 mm height, 3–3.2 cm diameter, margin lobed;interior annulus structure of similar size to the disk, 7 cm in diameter, reddish-brown in color, surface glabrous but hispidulous along the margin, grooves strap-shaped, 1.7 cm long, 0.4–0.5 cm wide; exterior annulus structure similar to the male flower, ovary 5 cm wide, 1.2 cm height, lunate–triangular, acutely angled. Fruit and seedsnot observed.