Inversodicraea tassing Cheek, 2019

Inversodicraea tassing Cheek View in CoL , sp. nov. — Fig. 3 View Fig , 4 View Fig

Differs from all other species of Inversodicraea in: a) the extreme length of the two styles, which equal or exceed the length of the ovary, and which at (2 –) 2.3 mm long, are nearly twice as long as the longest otherwise known in the genus ( 1.2 mm long); b) the scale-leaves are mainly restricted to a single whorl around the spathellum (not scattered on or densely covering the flowering shoot). — Type: Jennings 19 (holo K; iso HNG, WAG, ZT), Guinea,border of Kindia & Coyah Prefectures, Plateau de Tassing , N9°42'30" W13°12'49.5", above Fossikouré Village , top of the 270 m high ‘ Chute de Kili’ on the Kili River, fl. 7 Dec. 2017 GoogleMaps .

Etymology. Named in honour of the Plateau de Tassing, only known location for this species.

Perennial or annual herb, Root horizontal, dorsiventrally flattened, 1 – 1.5( – 2) mm wide, 0.5 – 1 mm thick, internodes 2 – 3 mm long, root branches opposite or alternate, sometimes subtending erect shoots. Stems 15 – 30 cm long, streaming in the water, terete, 1.5 – 2.5 mm diam along most of their length, internodes 3 – 7 mm long, phyllotaxy spiral, with 3 – 8 lateral branches each 1.2 – 6 cm long, mainly from the distal 1/2 of main axis. Spur-shoots single ( Fig. 3e View Fig ), in pairs ( Fig. 3d, h View Fig ) or in clusters of up to 10 ( Fig. 3c View Fig ), terete, 2 – 4 mm long, 0.55 – 0.7 mm wide at base, usually naked apart from a whorl of 5 – 7 scale-leaves at the apex. Scale-leaves dorsiventrally flattened, more or less appressed, quadrangular to oblong in outline, 0.5 – 1 mm long, 0.4 – 0.6 mm wide, divided by 1/3 to 9/10 into three subequal forward-directed, triangular lobes; scale-leaves absent from the principal axis, mostly only immediately below the flowering shoot apex, part covering the developing spathellum ( Fig. 3d View Fig ), both 3-lobed and entire, triangular-ovate 0.3 by 0.25 – 0.3 mm, apex obtuse to rounded. Sometimes additionally with several scale-leaves scattered along the length of the spur-shoot ( Fig. 3e View Fig ), or on the branch stems bearing the spur-shoots ( Fig. 3d View Fig ), however, the structures here called scale-leaves may in fact be the bases of fallen leaves. Leaves not sheathing, astipulate, dorsiventrally flattened, narrowly ribbon-like, 0.4 – 8.5 by 0.02 – 0.1 cm, towards the base more or less canaliculate, apex obtuse to acute; leaves at base of principal axis entire and short, extending in length towards the apex of the principal axes, and in the distal half becoming once-bifurcate, and ultimately twice-bifurcate, sometimes subtending lateral branches or spur-shoots ( Fig. 3e View Fig ) or inserted on a spur-shoot ( Fig. 3h View Fig ). Spathellum (pre-anthetic) oblong-ellipsoid 2.5 – 3 by 1.1 – 1.4 mm, mucro absent or obscure, stipe inconspicuous; post-dehiscence cylindric or narrowly funnel-shaped, 3.5 – 4.5 by 1.4 – 2 mm, with 2 – 4 irregular triangular lobes. Pedicel 11 – 12 mm long, 0.25 – 0.3 mm diam. Tepals 2, inserted opposite the base of the androecium, ligulate or slightly spatulate, 0.3 – 0.5 mm long, apex rounded. Androecium of 2 stamens, about as long as ovary; andropodium (united filaments) 1 – 1.2 mm long, free filaments 1.7 – 2.8 mm long, diverging; anthers 4-celled, 1.4 – 1.5 mm long, 0.4 – 0.5 mm wide. Gynoecium with gynophore 0.5 – 0.9 mm long. Ovary unilocular, narrowly ellipsoid in side view, 2.1 – 2.3 by (0.5 –) 0.7 – 0.8 mm, in transverse section isodiametric, with 8 equal longitudinal ridges (commissural ridges developed). Styles cream, as long as or exceeding ovary, narrowly cylindrical (2 –) 2.3 mm long, connate for the basal 0.2 mm, apex acute, 0.1 mm diam, surface minutely papillate. Fruit and seed not known.

Distribution — Guinea, border of Kindia & Coyah Prefectures, Plateau de Tassing.

Ecology — On rocks in fast-flowing water above waterfall at top of sandstone table mountain; 430 m altitude.

Conservation — Known from one location where currently there are no threats, but since a single event might eliminate the species globally, we here assess the species as Near Threatened. The area of occupancy is calculated as 1 km 2. Hundreds of individuals of this species were seen, but no other Podostemacaeae were present (Jennings pers. obs. 2017).

The river flows over flat sandstone bedrock along a fault line on the sandstone plateau. The river is about 10 m wide where the species grows, but divided into braided channels, each of which is only 0.5 – 1 m wide, and can be 1 m deep. Although fast-flowing, no white water was present at the time of collection. The plants were seen along c. 50 m along the river at this point (Jennings pers. obs. 2017). Suitable habitat for this species was seen on Google Earth, along the Kili River, up to several km upstream.

Notes — Inversodicraea tassing is unique in the genus for the extraordinary length of the styles, and for the restriction of the scale-leaves to the apex of the spur-shoots (see diagnosis). Its closest affinities may be with I. feika Cheek of Port Loko, Sierra Leone, since the two species have similar habit, branch- ing and leaf-arrangement, differing principally in the details of the flowers and the shape of the scale-leaves due to which they cannot be confused.