Namibithamnus H. Rob., Skvarla & V.A. Funk, 2016

Robinson, Harold, Skvarla, John J. & Funk, Vicki A., 2016, Vernonieae (Asteraceae) of southern Africa: A generic disposition of the species and a study of their pollen, PhytoKeys 60, pp. 49-126 : 80-81

Namibithamnus H. Rob., Skvarla & V.A. Funk gen. nov. Figures 15 C–D ; 16 F–H

Type.

Vernonia obionifolia O. Hoffm.

Descriptions.

Small aromatic shrubs to 1.5 m tall; stems, leaves, involucral bracts densely yellowish gray tomentellous or sericeous with crowded T-shaped hairs, hairs with slender 0-2-septate short stalks and small naviculiform or rather elongate cap-cells. Leaves alternate, short-petiolate, with small axillary fascicles usually present, more crowded proximally, smaller distally; blades 5-12 mm long, oblong to obovate, with undulate entire to coarsely dentate margins, basal pair of secondary veins scarcely evident or evident and strongly ascending, minute glandular dots densely disposed on both surfaces. Inflorescences appearing shortly scapose, with numerous pedunculate heads in a corymbiform or partly subumbellate arrangement. Heads campanulate, 6-7 mm wide and high; involucral bracts ca. 60 in ca. 6 strongly gradate series, persistent, oblong ovate with narrow apiculate tips, yellowish with reddish patch or midvein below tip, margins entire, broadly and distinctly thick and pale; receptacle convex, pitted with broad pale network of ridges. Florets 35-40 in a head. Corollas purple, narrowly funnel-shaped from a slender basal tube; throat twice as long as the erect, linear lobes, outer surface of base and throat mostly glabrous, lobes densely glandular-dotted; anther thecae narrow, slightly longer than throat, bases without tails, apical appendages shortly oblong-triangular, glabrous, with thin cell walls; style base with narrow annuliform node; with acicular sweeping hairs almost completely restricted to style branches, a few at top of shaft. Achenes 5-costate, with setulae not divided at tips, surfaces with numerous ungrouped idioblasts, raphids elongate; carpopodium turbinate, glabrous; pappus of ca. 35 slender persistent bristles, bristles as wide at tips as at base, densely scabrid on margins and outer surface, outer series of distinct, smooth, lanceolate scales. Chromosome number unknown.

Pollen ca. 45 μm in diam. in fluid, lophate, triporate, not echinate, perforated tectum restricted or lacking, crests of muri sparsely papillose (Fig. 16 F–H ).

Figures

Figure 15. Photographs of Linzia and Namibithamnus: A-B Linzia glabra Steetz in Peters, note that the flowers bloom in two groups with the outer ones blooming first (light colored in 15 B) followed by the innermost ones (dark purple in 15 B) C-D Namibithamnus obionifolius (O. Hoffm.) H. Rob. See Appendix C for citation details.

Figure 16. Scanning electron micrographs of Linzia and Namibithamnus pollen. A, B, E Linzia rosenii. (R. E. Fries) H. Rob., Skvarla & V. A. Funk. A Polar view B Equatorial view C Equatorial view. Note differences of lophae surrounding pores in B and C, D Linzia glabra Steetz in Peters. Lateral view. E Linzia rosenii. Fractured pollen wall. F-H Namibithamnus obionifolius (O. Hoffm.) H. Rob., Skvarla & V. A. Funk. F Equatorial view. This is the most common form of aperture G Equatorial view. Less common form of aperture with broken lophal arms apparent H Near polar view (A-C, E Jacobsen 3075 D West 7292 F-H Toelken & Hardy 770).