Hultholia E. Gagnon & G. P. Lewis, 2016

Gagnon, Edeline, Bruneau, Anne, Hughes, Colin E., de Queiroz, Luciano Paganucci & Lewis, Gwilym P., 2016, A new generic system for the pantropical Caesalpinia group (Leguminosae), PhytoKeys 71, pp. 1-160 : 39

10. Hultholia E. Gagnon & G. P. Lewis gen. nov. Figs 17 , 18

Diagnosis.

Hultholia is closely related and morphologically similar to Guilandina . While both genera form armed lianas, Hultholia differs in having stems with dome-shaped glands intermixed with dense slender, patent, needle-like prickles (vs. stems eglandular and with strongly recurved, robust prickles in Guilandina ); both genera have sharp recurved prickles on the leaf and pinnae rachises. Hultholia has bisexual flowers (vs. unisexual flowers on separate female and male racemes in Guilandina ), a zygomorphic corolla, with petals extending beyond the sepals, and the median (standard) petal smaller than the other four (vs. a sub-actinomorphic to zygomorphic corolla, with petals only slightly extending beyond the sepals in Guilandina ), unarmed, obovoid, falcate, pubescent, vesicular pods (vs. oblong-elliptic, coriaceous, eglandular, inflated pods, usually armed with 5-10 mm long, slender spinescent bristles), and sub-globose, oblong, grey, ca. 10 × 7 mm, smooth seeds (vs. obovoid to globular c. 20 mm in diameter, grey, pale to dark brown or orange seeds, with parallel fracture lines concentric with the small apical hilum).

Type.

Hultholia mimosoides (Lam.) E. Gagnon & G. P. Lewis ≡ Caesalpinia mimosoides Lam.

Description.

Climbing woody shrub; branches densely armed with short, robust, needle-like trichomes; young stems pubescent, with rust-coloured, hyaline hairs and dome-shaped glands, topped with a few hairs. Stipules subulate, 7-15 mm long, pubescent, caducous. Leaves alternate, bipinnate, without a single terminal pinna, 22-40 cm long; pinnae opposite, in 10-30 pairs per leaf, about 3-5 cm long, pubescent, with a pair of deflexed prickles at the insertion of the pinnae on the leaf rachis, and at the insertion of leaflets on the pinnae rachises; leaflets opposite, in 7-20 pairs per pinna, oblong, asymmetric at base, c. 9 × 4 mm, glabrous, eglandular. Inflorescences terminal or leaf-opposed, lax racemes, with 50 or more flowers, 20-40 cm long; rachis and pedicels armed with needle-like, robust trichomes, pubescent and covered with domed, hair-tipped glands. Flowers bisexual, zygomorphic; calyx comprising a hypanthium with 5 sepals 13-16 × 6 mm; hypanthium and sepals pubescent and glandular, the sepal margins sometimes with small stipitate glands, <1 mm long; petals 5, free, bright yellow, dark glands present on the blade, median (standard) petal c. 8 mm wide and smaller than the 4 lateral petals, that are c. 1.7 × 1.3 cm; stamens 10, free, filaments 1.8 cm long, pubescent at least on the lower ½; ovary densely pubescent, and with glandular dots (often obscured by the dense pubescence). Fruit an obovoid, falcate, vesicular, unarmed, dehiscent pod, sparsely pubescent, particularly along the margin, and with a few obscure stellate hairs, and covered in gland dots, 5-6 × 2.5-3 cm, 1-3-seeded. Seeds sub-globose, oblong, 10 × 7 mm, grey.

Geographic distribution.

The single species is distributed across Asia, in China (Yunnan), Bangladesh, India, Laos, Myanmar (Burma), Thailand and Vietnam.

Habitat.

In secondary thickets and clearings, often on roadsides, up to 1500 m elevation. More information on the ecology of this genus is needed.

Etymology.

The name Hultholia honours the Cambodian botanist Dr. Sovanmoly Hul Thol (born 1946), whose doctoral thesis, "Contribution à la révision de quelques genres de Caesalpiniaceae , representés en Asie" (1976), is an important revision of the Asian species and genera of the Caesalpinia group, and particularly the genus Pterolobium . Dr. Hul Thol retired from the Museum National d’Histoire Naturelle, Paris in 2014, but continues as an honorary researcher. She is a specialist on the flora of Cambodia and South East Asia, directed the publication of multiple volumes of the Flora of Cambodia, Laos and Vietnam from 1995, and is one of the co-founders of the National Herbarium of Cambodia, Royal University of Phnom Penh.

Notes.

Although Hultholia mimosoides is not known to be cultivated, the young, pungent, flowering shoots are sold as a vegetable in markets in Vientiane (Laos) ( Vidal and Hul Thol 1976).

References.

Vidal and Hul Thol (1976); Chen et al. (2010a: 42-43).

Figures

Figure 17. Hultholia mimosoides (Lam.) E. Gagnon & G. P. Lewis. A habit, including foliage and inflorescences B stem armature detail C bud showing cucullate lower lobe of calyx D calyx lobes outer surface E calyx cucullate lower lobe side view, F median petal inner surface G median petal side view H upper lateral petal inner surface I lower lateral petal inner surface J stamens K anthers dorsal and ventral views L gynoecium M stigma detail N fruit O seed. A-K from Clark 237 L, M from Beusekom & Geesink 4706 N, O from Bunchuai 1342. Drawn by Juliet Williamson.

Figure 18. Hultholia mimosoides (Lam.) E. Gagnon & G. P. Lewis. A young leaves and inflorescence in bud (J. Jose, Wikicommons (https: // commons. wikimedia. org / wiki / File: Caesalpinia _ mimosoides _ 2 _ at _ Kudayathoor. jpg), Kerala, India, unvouchered) B flower (R. Clark, Thailand, Clark et al. 237 (K )) C flowers D immature fruits E mature fruit F habit G open fruit with seeds (V. R. Vinayaraj, Wikicommons (https: // commons. wikimedia. org / wiki / Category: Caesalpinia _ mimosoides, the basionym of Hultholia mimosoides), India, unvouchered).