Vernoniastrum H. Rob., 1999

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 : 93-94

Vernoniastrum H. Rob., 1999 Figures 23 F–G ; 25 D–I

Vernoniastrum H. Rob.. Proc. Biol. Soc. Wash. 112(1): 233. 1999. - Type: Crystallopollen latifolium Steetz in Peters.

Vernonia sect. Lepidella Oliv. & Heirn, Fl. Trop. Afr. 3: 267. 1877, non Lepidella Tiegh. 1912 or Lepidella E.J. Gilbert 1925. - Type: Vernonia petersii Oliv. & Hiern.

Vernonia subsect. Lepidella (Oliv. & Hiern) S.B. Jones, Rhodora 83: 72. 1981.

Descriptions

. Annual or perennial herbs 0.3-1.0 m tall; stems pilose, hairs simple with elongate apical cells with slightly asymmetric bases. Leaves alternate. Inflorescence with 1-many heads. Involucre campanulate; involucral bracts ca. 50 in ca. three series, gradate, persistent; receptacle epaleaceous. Florets ca. 50 in a head; corollas reddish-purple, basal tube narrowly funnelform, throat shorter than lobes or anther thecae, lobes pilosulous distally; anther bases acuminate to acutely tailed; apical appendage glabrous, with thin cell walls. Style base with node; style branches with acicular sweeping hairs. Achenes 4-6-angled, setulae aparse on sides, idioblasts usually grouped in transverse bands, raphids elongate; pappus bristles subpersistent, marginally densely barbellate; outer squamae persistent. Chromosome number n = 10 ( Jones 1979, 1982).

Pollen triporate, lophate, perforated tectum discontinuous in lacunae, muri papillate, with or without micropunctations on muri (Fig. 25 D–I ).

With habit similar to Polydora but often perennial, lacking L-shaped hairs, having tailed anther bases, and a chromosome number n = 10. Also characteristic of the core element of Vernoniastrum are the transverse bands of crowded idioblasts in the achene walls.

Figures

Figure 23. Photographs of Pseudopegolettia and Vernoniastrum: A-C Pseudopegolettia tenella (DC.) H. Rob., D-E Pseudopegolettia thodei (Phillips) H. Rob., Skvarla & V. A. Funk, note: images show the leafy stem of Pseudopegolettia tenella and the succulent basal leaves of Pseudopegolettia thodei; F-G Vernoniastrum latifolium (Steetz in Peters) H. Rob .. See Appendix C for citation details.

Figure 25. Scanning electron micrographs of Vernonella and Vernoniastrum. A-C Scanning electron micrographs of acetolyzed sublophate-echinolophate pollen of Vernonella africana Sond. A Polar view B Equatorial view C Oblique polar view. A-C from Wood 753. D-I Scanning electron micrographs of acetolyzed echinolophate pollen of Vernoniastrum nestor (S. Moore) H. Rob., showing diversity of lacunae and lophae. D-H Oblique and near polar views showing apertures in markedly long lacunae with irregular lophae H Lateral view with apertures (arrows) occupying long lacunar spaces I Enlarged section of surface showing columellae in irregular rows under muri). D-I from Reekmans 9185.