Occultia Stedje & Rulkens, 2022

Stedje, Brita, Rulkens, Antonius J. H. & Hankey, Andrew J., 2022, Occultia (Scilloideae, Asparagaceae), a new genus from Malawi and Mozambique, Phytotaxa 575 (2), pp. 166-172 : 167-168

Occultia Stedje & Rulkens genus nov. ( Figs. 1–3 )

Similar to Ledebouria , but differing by tepals being united into a tube for 1/3 to half their length (not free); the filaments are adnate to tepals, with the free portions being very short and arising from the tepals tube at two levels (not free and inserted at the base); the developing capsule has a cap composed by the withered tepals that with development detaches from the basis, becomes membranous and finally falls off (no cap formed, tepals fleshy if persistent).

Type: — Occultia ledebourioides (Baker) Stedje & Rulkens (holotype, K!, lectotype) ≡ Hyacinthus ledebourioides Baker

Short bulbous herbs. Bulb ovoid to subglobose with pale and papery outer scales, and thick and white inner scales. Leaves one to several, linear to ovate, often with a distinct pseudopetiole; lamina glabrous, green, sometimes spotted darker green adaxially or sometimes with purple markings at base or abaxially. Peduncle erect to slightly curved, usually somewhat longer than the leaves. Inflorescence a short raceme, relatively lax with up to 40 flowers; pedicels patent to erecto-patent, short. Perianth campanulate, white and green to pinkish, about 4 mm long; united into a tube for 1/3 to half its length, free parts spreading. Stamens adnate to tepals and free portions very short making the anthers look as they are almost sessile and arising in two levels from top of tepals tube ( Fig 1B ). Ovary sessile, subglobose. Fruit a depressed globose and emarginated capsule. When the capsule develops, the perianth is detached from its basis, becomes membranous and falls off early, or sometimes forms a cap on the developing capsule ( Figs. 1D , 3C ). Seeds mostly one per locule, sometimes two, globose or subglobose, if two in a locule somewhat flattened at one side.

Etymology: —“ Occultia ” is derived from the Latin verb “occulere”, meaning: “to conceal”. Plants of this genus are concealed in several ways. Plants are very small and are thus easily overlooked. Also, leaves and other aboveground plant parts are produced for a very short time span every year. Finally, at first sight these plants may easily be confused with Ledebouria unless the tiny flowers are carefully examined.

Distribution: —Southern Malawi, central and north-eastern Mozambique. In Mozambique, plants of the genus Occultia have been observed by one of the authors (A. Rulkens) in the provinces of Sofala, Zambezia, Nampula and Cabo Delgado. In Malawi, the genus is distributed in the central and southern regions.

Taxonomic and phylogenetic note: —This new genus is clearly separated from Ledebouria , Drimiopsis and Resnova in floral characters. Even if these three genera may show tepals united at the base, the tepals tubes never reach 1/3 to half of the tepals length (measured on softened flowers of herbarium specimens), and the stamens are always inserted at the base of the tepals or very close to the base. The filaments are very short in Occultia and have a certain length in Ledebouria . Furthermore, the tepals of Occultia become membranous and detached from their basis, but may form a cap on the developing capsule. Those of Ledebouria and Drimiopsis are, if persistent on the developing capsule, always attached to the base of the capsule and may become fleshy with time, never forming a membranous cap.

Diagnostic key

So far, two species are recognized in Occultia . They can be separated based on leaf characters, flower colour and ecology.

1. Leaves 3 or more, narrowly lanceolate, erect, up to 10 mm wide; flowers pinkish; growing on shallow rocky and wet ground ...... ............................................................................................................................................................................. 1. O. ledebourioides

2. Leaves usually one (rarely 2 or 3), widely lanceolate to ovate, flat on the ground; flowers white, turning greenish towards the base; growing on humus-rich shady underground of Mopane woodland............................................................................... 2. O. fragrans

Figures

FIGURE 1. Occultia ledebourioides (specimen Rulkens 17A).A:Entire plant; B: Flower, side view; C: Flower from above, D:Developing capsule. Scale bars 20 mm (A) and 2 mm (B–D).

FIGURE 2. Occultia fragrans, entire plant (specimen Rulkens 50). Scale bar 20 mm.

FIGURE 3. A–B: Occultia ledebourioides (specimen Rulkens 17A). A: Entire plant in flower: B: Close up of flowers where one whorl of stamens can be seen in the mouth of the perianth tube, the other partly hidden in the perianth tube. C: O. ledebourioides, (specimen Rulkens 106), entire plant in fruit. D–F: O. fragrans, (specimen Rulkens 50). D: Entire plant in flower; e: Close up of flower; F: Leaf. All photos:A.J.H. Rulkens. Scale bars 20 mm (A, C and F) and 2 mm (B and E).