Typhonium obtusum Luu, X.B.Nguyen-Le & H.C.Nguyen, 2024

Luu, Hong Truong, Nguyen-Phi, Nga, Nguyen, Quoc Dat, Nguyen, Hieu Cuong, Van, Hong Thien & Nguyen-Le, Xuan Bach, 2024, A new species of Typhonium (Araceae) from Vietnam, PhytoKeys 238, pp. 119-126 : 119

Typhonium obtusum Luu, X.B.Nguyen-Le & H.C.Nguyen sp. nov.

Fig. 1

Type.

Vietnam. Phu Yen Province, Tay Hoa District, Hoa Thinh Ward; 12°54'30.1"N, 109°14'15.1"E, 30 m elevation; 5 August 2015; Nguyen Le Xuan Bach & Nguyen Hieu Cuong PY495-505 (holotype SGN!; isotypes SGN!, PHH!) .

Diagnosis.

Typhonium obtusum is morphologically similar to T. rhizomatosum and T. cordifolium in having ovate leaf blades with cordate base, oblong and elongate spathe limb as long as the spadix and an elongated fusiform spadix appendix. However, the novel taxon can be distinguished from T. rhizomatosum by its subcylindrical (vs. globose to subglobose) tubers without (vs. with) rhizomatous offsets, stipitate and fusiform (vs. sessile and conical) spadix appendix) and oblong-elliptic (vs. narrowly triangular ovate) spathe limb and from T. cordifolium by its subcylindrical (vs. subglobose) tubers, leaves without (vs. with) adventitious buds, oblong-elliptic (vs. narrowly triangular ovate) spathe limb and stipitate and fusiform (vs. sessile and cylindrical) spadix appendix.

Description.

Herbs, seasonally dormant, 10-17 cm tall; tuber underground, subcylindrical, fleshy, 2-2.5 cm long, 1-1.5 cm in diameter, with many filiform roots. Leaves 2-3 together. Petiole smooth, slender, 5-9 cm long, 1.8-2.2 mm in diameter, white to brown at base, green towards the apex. Leaf blade entire or trilobate, strongly cordate, glabrous, adaxially green, abaxially lighter green, concave, 3.2-4.7 cm long, 3-4 cm wide; entire leaf blade ovate, rounded at apex, venation pinnate with abaxially prominent midrib, lateral veins 5-8, brochiododromous, collective veins at 2-5 mm from margin; anterior lobes ovate, broadly elliptic to obovate, 2.5-3.7 cm long, 2.3-3.0 cm wide, obtuse to rounded at apex with a minute mucro, mid-rib abaxially prominent, lateral veins 4-6, brochiododromous, collective veins at 1-2 mm from margin; lateral lobes elliptic to ovate, 2.2-3.1 cm long, 0.6-1.6 cm wide, obtuse at apex, oblique at base. Inflorescences solitary; peduncle white, 2.5-6 cm long, ca. 4 mm in diameter; spathe 5-6 cm long, tube and limb separated by a constriction, outside green-brown, inside purple-brown; spathe tube ovoid, 1.1-1.3 cm long, 7-8 mm in diameter; spathe limb oblong-elliptic, 4-4.5 cm long, 1.1-1.3 cm wide, obtuse at apex, hardly open at base at anthesis; spadix equal or slightly shorter than spathe, sessile; female part conical, 1.6-2 mm long, 3.9-4.3 mm in diameter at the base, 2-3 mm in diameter at the top, with 3-4 rows of crowded pistils; ovary obovate, ca. 1 mm long, 0.6-0.8 mm in diameter, yellowish-greenish, with purple spots, unilocular, uniovulate placentation, transparently white; ovule light yellow, on a basal placenta and hold obliquely on a funicle; stigma sessile, disciform, 0.3-0.5 mm in diam., 0.1-0.2 mm high, light yellow, penicillate; interstice 1-1.3 cm long, lower part ca. 4 mm densely covered with staminodes, upper part naked, smooth, white to yellowish; staminodes filiform, subulate, 1-3 mm long, 0.4 mm in diameter, apically curved downward, yellowish-greenish; male part cylindrical, ca. 4.5 mm long, ca. 2.5 mm in diameter; stamens free, sparsely to (mostly) densely arranged; thecae globular, ca. 0.3 mm in diameter, dark purple, opening by apical slit; pollens translucent white; appendix stipitate, elongated fusiform, pale yellowish, 2.5-3.9 cm long, 2-3 mm in diameter, stipe ca. 3.5 mm long, pale yellow. Fruits ovoid to capsule-shaped, 3-4 mm long, 1.5-1.8 mm in diameter, white at base, green towards the apex with many dark purple spots.

Etymology.

The species is named for the obtuse apex of its spathe limb.

Vernacular name.

Bán hạ mo tù (Vietnamese); Obtuse-spathed typhonium (English, here proposed).

Ecological notes.

The new species was found growing in clumps on basalt soils in open places of rural farms. It appears in September to December and becomes dormant in January to August. Flowering and fruiting were seen in August.

Distribution.

Typhonium obtusum has been recorded only from the type locality.

Conservation status.

Data Deficient (DD) ( IUCN Standards and Petitions Subcommittee 2022). The new species has, so far, been found in one location and further inventory should be employed for a certain assessment.

Taxonomic notes.

The key morphological similarities and differences of T. obtusum versus T. rhizomatosum and T. cordifolium are presented in the diagnosis. In addition, the two latter are different from the new species by their unique characters in the genus: T. cordifolium with adventitious buds appearing at the mature leaf blade apex or sometimes at the top of the sheath, while T. rhizomatosum often forms large colonies thanks to its rhizomatous offsettings ( Murata et al. 2010; Boyce et al. 2012; Nguyen-Phi et al. 2023).

The new species may be morphologically close to T. hayatae Sribonnma & J.Murata ( Sriboonma et al. 1994), T. inopinatum Prain ( King and Prain 1898), T. medusae Hett. & Sookch. ( Hetterscheid et al. 2001) and T. varians Hett. & Sookch. ( Hetterscheid et al. 2001), as they have a short spathe limb and similar general shape and structure of the spadix and filiform staminodes. However, these species are easily distinguishable from the new taxon as they have elongate conical, sessile or shortly stipitate spadix appendix with truncate base. Furthermore, T. hayatae has globose tuber, long spadix appendix (6-14 cm) and spathe limb (12-26 cm); T. inopinatum has globose tuber, ovate-lanceolate spathe limb that is shorter than the spadix appendix and yellow staminodes; T. medusae has depressed tuber, velvety petioles, hairy leaf blades, orbicular spathe limb, pale yellow or cream staminodes and elongate conical appendix; T. varians has depressed tuber, dark grey spadix appendix 4.5-9 cm long, triangular ovate spathe limb of 7-14 cm length and 4-7.5 cm in diameter and pale pink anthers. Their different morphological characters are summarised in Table 1 .

Key to the 24 presently known Vietnamese species of Typhonium

1	Sterile interstice of spadix entirely covered with staminodes	T. flagelliforme
-	Only base of sterile interstice of spadix covered with staminodes	2
2	Leaves perfectly trifoliolate	3
-	Not as above	4
3	Plant with 3 leaves; appendix stipitate; female section of spadix with 5-6 rows of pistils	T. thatsonense
-	Plant with 1 leaf; appendix sessile; female section of spadix with 2-3 rows of pistils	T. hangiae
4	Inflorescence appearing before the leaves	5
-	Inflorescence appearing together with the leaves	6
5	Spathe 6-9 cm long; staminodes ca. 6 mm long	T. penicillatum
-	Spathe 14-30 cm long; staminodes ≤ 3 mm long	T. hayatae
6	Spathe limb elongate, narrowly lanceolate-triangular	7
-	Spathe limb wide, oblong-elliptic, ovate to lanceolate	15
7	Staminodes red with a light yellow acumen	8
-	Staminodes unicolourful	9
8	Spathe tube globose, to 1.5 cm long; staminodes 5 mm long, clavate	T. bachmaense
-	Spathe tube oblong or cylindrical, 2 cm long; staminodes 12 mm long, acute	T. kbangense
9	Spathe limb white	T. praelongum
-	Not as above	10
10	Spathe limb corrugated	T. corrugatum
-	Not as above	11
11	Leaf 3-lobed	12
-	Not as above	13
12	Stigma funnel-shaped and lobed	T. stigmatilobatum
-	Stigma disciform and unlobed	T. huense
13	Leaves with 7 leaflets, leaflets linear to or linear-lanceolate	T. lineare
-	Not as above	14
14	Spathe limb much shorter than spadix appendix	T. vermiforme
-	Spathe limb as long as spadix appendix	T. dongnaiense
15	Spadix longer than spathe	16
-	Spadix as long as or shorter than spathe	18
16	Staminodes folded 180° apically	T. phuocbinhense
-	Staminodes straight up to parallel to axis	17
17	Male zone cylindrical, staminodes cylindrical to conical	T. khonkaenensis
-	Male zone subglobose, staminodes clavate	T. acetosella
18	Leaves developing bulbils at the top and/or the base, upper surface ften grey variegated	T. cordifolium
-	Not as above	19
19	Spathe limb very strongly circinnately recoiled over the entire length	T. circinnatum
-	Not as above	20
20	Tuber producing rhizomatous offsets about 5 cm apart	T. rhizomatosum
-	Not as above	21
21	Staminodes ≤ 3 mm long	22
-	Staminodes> 5 mm long	23
22	Spathe tube above the ground; spathe limb oblong-elliptic, with obtuse apex	T. obtusum
-	Spathe tube underground; spathe limb triangular ovate, with acute apex	T. vietnamense
23	Staminodes red with a light yellow acumen, upward straight or slightly curved	T. blumei
-	Staminodes whitish, curly	T. trilobatum

Figures

Figure 1. Typhonium obtusum A whole plants B stem C different forms of leaf blade D inflorescence E spathe and spadix F male, sterile and female zones G stamens H thecae, opened I pistils, cross-dissection J fruits.