Squamellaria kajewskii (Merr. & L.M.Perry) Chomicki

54. Squamellaria kajewskii (Merr. & L.M.Perry) Chomicki View in CoL — Fig. 57 View Fig , 58 View Fig

Squamellaria kajewskii (Merr. & L.M.Perry) Chomicki in Chomicki & Renner (2016) 20; Hydnophytum kajewskii Merr. & L.M.Perry (1945) 25. — Type: Kajewski 1716 (lectotype A; iso BM, BO, BRI, G, P), Bougainville, Kupei Gold Field, 14 Apr. 1930.

Tuber scaphoid, with a flattened to sunken upper surface, and a broad, keeled, swollen and bellying lower surface; obovate from above, and triangular-obovate to cordate in transverse section; to 19 cm long, 12 cm wide and 10 cm deep. Initial tuber (basal) cylindrical, with small lipped entrance holes 1–4 mm diam in a row along each side. Initially horizontal, ascending and becoming almost vertical, and then thickening greatly, and becoming triangular in section with a flattened dorsal surface, before turning sharply downwards and horizontal once more. Mature part of tuber with 2 rows of prominently lipped entrance holes along upper, outer edges, 1–2.5 cm diam, and 1 cm apart, with lips to 0.5 cm thick, pointing outwards to downwards. Older tubers may loose this symmetry and become more rotund with additional rows of entrance holes. Tuber surface smooth, dark-brown, dull, with small roots and tubercle-like swellings, especially on upper surface and towards base; keel with very slight corrugations corresponding to cavities within. Entrance holes each giving rise to a transverse warted chamber, and paired to an entrance hole on the opposite side of tuber; each chamber having 2 entrance holes. Cavity walls dark in upper parts, pale below; warted throughout, warts root-like in clusters of 2–5, most numerous above, on dark-coloured walls. Stems several, arising from a common stock; to 80 by 0.3 cm; branching; older stems with annular furrows, younger stems drying ridged, dark-brown to black. Internodes 0.5–7 cm in length, generally shortest towards shoot apex, nodes swollen.A pair of rounded ridges descending from stipules. Leaves sessile. Lamina subrotund, 2 by 1.2 to 4 by 3 cm; apex acute to blunt; base blunt to cordate; midrib prominent below, less so above; veins 5–7 prominent above and below. New leaves white to very pale green, when mature medium green, upper surface dull, lower surface with a slight sheen; drying dark green above, pale below, new leaves drying translucent. Stipules acuminate to 0.1 cm, persistent. Inflorescence solitary, pedunculate; initially terminal, becoming axillary, slightly offset to petiole. Peduncle to 2.5 by 0.2 cm; flattened; with two narrow and opposite ridges; with two, or rarely three, terminal, flower-bearing branches. Occasionally a single flower may be borne at centre of branch point. Side branches are narrow at their base, to 0.1 cm, becoming thicker above to c. 0.25 cm diam, when fertile. Flowers produced sequentially from individual sections of this peduncle, bracts minute. Flowers [8] heterostylous. Calyx to 1.5 mm, entire. Corolla tube 9 mm long, with a broad ring of hairs to 2 mm in breadth at mouth; lobes to 3 by 1 mm, recurved in open flower, uncus to 0.5 mm. Short-styled flowers with anthers to 1 mm, exserted; filaments to 3 mm; pollen 53–60(–69) μm, walls c. 4.4 μm thick, brochi 1 μm, pores 15–23 μm across; style 7 mm in length, stigma 2-fid, below mouth of tube. Long-styled flowers with anthers to 1 mm; within mouth of corolla tube; filaments <0.5 mm; pollen 47–53 (51) μm, walls c. 3.75 μm thick, pores 11–16 μm, reticulation fine, brochi to 1 μm, lacking vesicles; stigma 2-fid, well exserted from mouth, stigma 2-fid, papillose. Fruit flattened turbinate; to 9 by 5 mm; with prominent calyx remains; red, with distinct white lines when ripe. Pyrenes obovoid, to 7 by 2.5 mm; apex rounded, base tapered.

Ecology & Habitat — Ants have been recorded in certain collection notes, but are not present in the tubers which collect rainwater (being water-filled when collected, MHPJ pers. obs.). Although the cavity openings do not appear ideally suited for this (they point sideways or downwards, and have a large swollen lip), there seems little doubt they function as such. Cockroaches are commonly found in these cavities along with their egg cases. The species is found in similar habitats to S. guppyana , but tends to be observed higher in the canopy.

Distribution — Papua New Guinea (Bougainville), Solomon Islands (Santa Isabel).

Conservation status — Vulnerable (VU) under criteria B1ab(iii) +2ab(iii). This species is found on Bougainville with a single outlier on Santa Isabel island 500 km away. The Bougainville collections represent five locations (subpopulations) and taken alone they have an AOO (using an auto-value cell width of 5 km) of 112 km 2 and an EOO of 270 km 2. Other information EOO 7 500 km 2.

Notes — The tuber of this species is unique in its bilateral symmetry, having no parallel within the Hydnophytinae . However, with age the tuber acquires a more irregular appearance and looses its strikingly scaphoid form. It is commonly found growing with S. guppyana [53] from which it can be distinguished by its tuber, its smaller, more slender stems, smaller leaves, and its smaller, less-branched inflorescence, with long slender flowers.As a consequence, it is no surprise that Guppy collected both species as a mixed collection (see notes under S. guppyana ).

The cavity architecture of this species and S. guppyana have much in common, even though externally they are quite unalike. Both have a series of independent transverse cavities, each of which is added apically to the tuber. Each of these cavities comprises a broad chamber occupying almost the entire breadth of the tuber, from this arise narrow, tubular tunnels which run towards the tuber base (Jebb 1985, 1991a).