Vernonia potamophila Klatt, 1890

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 : 96-97

Vernonia potamophila Klatt, 1890

Vernonia potamophila Klatt, Annal. Naturh. Hofmus. Wien 7: 100. 1890.

Distribution.

Congo, Angola, Namibia (Caprivi strip), Zambia.

Descriptions.

The initial assumption, based on the robust habit and the described yellowish brown velutinous pubescence of the stems, was of a relationship to the genus Gymnanthemum of the subtribe Gymnantheminae . Other features indicate a different relationship. A high resolution image of an herbarium specimen (PRE; Fig. 2D ) as well as an illustration (Fig. 26 ), show a somewhat keeled involucral bract with a dark median stripe, a character not found in Gymnanthemum . In addition, the pollen totally lacks the strongly developed sublophate pattern that is characteristic of Gymnanthemum (Figs 10 A–C ) and instead is sublophate with small incipient lacunae (Fig. 27 ). The pollen and involucre characters seem to indicate a position in the subtribe Erlangeinae . This is most likely a new genus but without a more comprehensive study of the more northern members of the African Vernonieae we can only say that Vernonia potamophila , while definitely not a true Vernonia , is unplaced as to genus.

An examination of limited fragments showed a few additional characters. The abaxial surface of the leaf has a tomentum of long-armed T-shaped hairs and sweeping hairs restricted to the branches of the style and the juncture of the branches at the shaft of the style. The lobes of the corolla had areolae that were reminiscent of the ducts in the corolla lobes of true Vernonia , but the areolae do not form continuous elongate ducts. Raphids of the achenes were short-rectangular in elongate cells. Chromosome number unknown.

Figures

Figure 2. Illustrations: A Baccharoides adoensis (Sch. Bip. ex Walp.) H. Rob. B Bothriocline aggregata Hutch., note: this taxon is not found in southern Africa C Ethulia conyzoides L. f., note: lack of pappus; and D Gymnanthemum koekemoerae H. Rob. & V. Funk, note: broad involucral bracts without a high midrib. See Appendix C for citation details.

Figure 10. Scanning electron micrographs of acetolyzed pollen of two collections of sublophate echinolophate Gymnanthemum capense (A. Spreng.) J. C. Manning & N. Swelankomo. A Polar view B Equatorial view C Lateral view D Fractured grain structure of exine surfaces E Fractured grain showing spine construction. (A-C Schlechter 6644).

Figure 26. Illustration of Vernonia potamaphylla Klatt. See Appendix C for citation details. 1 Habit showing pinnate leaf veination 2 Involucral bracts showing keel and dark line 3 Floret with immature achene 4 Corolla opened longitudinally 5 Anthers 6 Style 7 Achene with pappus 8 Enlarged pappus bristle.

Figure 27. A-D Scanning electron micrographs of acetolyzed sublophate pollen of Vernonia potamaphylla Klatt. A Polar view B Equatorial view C Lateral view D Grain fragment. From Killick & Leistner 3277.