A review of the Litanthus group of Drimia Jacq. (Hyacinthaceae: Urgineoideae) with the description of a second species, Drimia stenocarpa, from Western Cape

Abstract We review the Litanthus group of Drimia and describe a second species from Western Cape, Drimia stenocarpa, differing from Drimia uniflora in its invariably solitary leaf, larger flowers with narrower tepal lobes, longer and thicker pedicels, and distinctive cylindrical–prismatic capsule longitudinally banded in green and white. Both species are fully described and illustrated and a distribution map is provided.


Introduction
The genus Drimia Jacq. sensu lat. comprises ±100 species of largely deciduous geophytes distributed throughout Africa and extending into Eurasia and the Indian subcontinent (Manning et al., 2004). In this broad circumscription it is characterised by the lower floral bracts (at least) bearing a small or large spur and by short-lived flowers with a ± gamotepalous perianth. In this sense it includes the genus Urginea Steinh., as well as several smaller groups of species previously segregated at generic level. Among the best known of these are Rhadamanthus Salisb., Schizobasis Baker, Thuranthos C.H. Wright, Tenicroa Raf. and the monotypic Litanthus Harv. Additional segregates have been recognised since then (see Speta, 1998) but have not been generally adopted. The majority of the southern African species in the group were last revised by Jessop (1977), supplemented by revisions of Rhadamanthus by Nordenstam (1970) and Tenicroa [as Sypharissa Salisb.] by Obermeyer (1980). Several new species have since been described and even the relatively recent checklist by Manning and Goldblatt (2003) is outdated. A modern review of the species and an infrageneric classification are urgently required. Here we review the species previously treated as the genus Litanthus.
Litanthus was described by Harvey (1844) for the new species Litanthus pusillus Harv. [now Drimia uniflora J.C. Manning & Goldblatt] and diagnosed by its 1(2)-flowered inflorescence terminated by a pair of subopposite bracts subtending a distinctive, cylindrical, pendulous flower with well-developed perianth tube [at least twice as long as the tepal lobes]. Typically only a solitary flower develops and the second bract is usually empty. An additional unusual character for the genus not commented on before is the prolongation of the anther connective into a small, translucent, membranous flap. We have observed this in no other species of Drimia with the notable exception of D. cuscutoides (Burch. ex Baker) J.C. Manning & Goldblatt. Litanthus was formally included in Drimia by Goldblatt and Manning (2000), at which time it was still monotypic.
Originally described from plants collected near Port Elizabeth, D. uniflora is now known to be widespread in southern Africa, ranging from Northern and Western Cape in South Africa to Zimbabwe (Jessop, 1977;Manning et al., 2002). Specimens collected near Papendorp in 1971by Harry Hall (1906-1986, formerly horticulturist at Kirstenbosch National Botanic Garden, were initially considered to represent a new species of Litanthus but were subsequently included in L. pusillus [now D. uniflora] by Jessop (1977) in his review of the group. Further collections of these diminutive plants made since then suggest that the initial South African Journal of Botany 90 (2014) 96-100 surmise was correct and that the Papendorp plants, along with additional populations from the Breede River in Western Cape, do indeed constitute a separate species, which we describe here as Drimia stenocarpa for its distinctive capsules. These populations differ most strikingly from D. uniflora in their prismatic, strongly bicoloured capsules on longer, stouter pedicels, and in their narrower tepal lobes. D. stenocarpa is restricted to the extreme southwestern, winter-rainfall parts of South Africa, with true D. uniflora occurring further to the north and east. We review and illustrate both species, based on herbarium and field studies.

Materials and methods
All relevant types were examined, as well as herbarium material from BOL, NBG, PRE and SAM (acronyms after Holmgren et al., 1990), the primary collections of southern African species. Both species were also studied in the field.

Species descriptions
Distribution and ecology: widespread through the drier, aseasonal and summer-rainfall parts of South Africa, from the Gamsberg in Bushmanland and the Little Karoo through the eastern half of the country into southern Zimbabwe but evidently absent from the more arid central region (Fig. 2). The diminutive plants typically grow in rock crevices or rocky cliffs, in seasonally damp situations generally in protected or sheltered locations, sometimes in mats with moss or other dwarf succulents.
Diagnosis and relationships: distinguished from D. stenocarpa by the small, globose bulbs and slightly smaller flowers, 4-6 mm long with ovate tepal lobes ± 1 mm long, and the ovoid or subglobose, unicoloured capsules ± 3 mm long. The pedicels, 0.5-1 mm long in flower, elongate hardly at all in fruit, reaching at most 2 mm long. Bulbs produce up to five threadlike leaves, only rarely just one.
The diminutive size of the species impressed Harvey (1844), who commented on the bulb as being scarcely larger than a good sized pea' and the scape as 'no thicker than a bristle'. Its relationships puzzled both Zehyer and Harvey (1844). The curious inflorescence with two, opposite bracts and the solitary, cylindrical flower misled Zehyer into considering it to be a dwarf species of Amaryllidaceae, as evinced by his annotation of his collection with the manuscript name Cyrtanthus minimus. Harvey (1844) correctly recognised its family affiliations but was misled by the tubular flower to relate it to the genus 'Uropetalum' [Uropetalum Burch. ex Ker Gawl.], now a synonym of Dipcadi Medik.  long; anthers erect forming cylinder, dorsifixed, thecae 1.0-1.5 mm long with connective extended apically into small, acute, membranous flap, sagittate, longitudinally dehiscent. Ovary cylindrical, 2-3 mm long, greenish yellow; style columnar, 2.0-3.5 mm long, slightly shorter than to slightly longer than ovary, extending shortly beyond anthers, white, stigma subcapitate, minutely 6-toothed, teeth erect. Capsule erect on erect pedicel, oblong-prismatic, 4-6 × ±2 mm, strongly bicoloured, dark greyish green with broad whitish longitudinal band along carpel sutures. Seeds angular, ±1 × 0.5-1 mm, glossy black, irregularly folded, testa finely rugulose. Flowering time: December to March (Fig. 3).
Distribution and ecology: known from three localities in the winterrainfall region of Western Cape, from Papendorp at the mouth of the Olifants River in southern Namaqualand, and from near Robertson and Malgas along the Breede River (Fig. 2). Plants are recorded from exposed sites, either on open flats in loamy soils or in rock crevices in shale, typically among various dwarf succulent species.
Diagnosis and relationships: distinguished from D. uniflora by the larger, ± pyriform bulbs with the outer tunics forming a welldeveloped, wrinkled neck, the slightly larger flowers, 6-7 mm long with lanceolate tepal lobes ± 2 mm long, and especially by the distinctive capsules. These are cylindrical-prismatic and 4-6 mm long and strikingly bicoloured, dull greyish green with broad, whitish longitudinal bands along the carpel sutures. Longer and stouter than in D. uniflora at all stages, the pedicels, 1-2.5 mm long at anthesis, elongate significantly in fruit, reaching 5-8 mm long. Plants appear to consistently produce just a solitary, terete leaf.