Polydora Fenzl, 1844

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 : 89-90

Polydora Fenzl, 1844 Figures 20 C–F ; Fig. 22 A–C

Polydora Fenzl, Flora 27: 312. 1844. - Type: Polydora stoechadifolia Fenzl = Webbia serratuloides DC.

Crystallopollen Steetz in Peters, Reise Mossamb. Bot. 363. 1864. - Type: Crystallopollen angustifolium Steetz

Resources.

Some species of the genus are treated by Pope (1986).

Descriptions.

Mostly annuals; stems with L-shaped hairs bearing elongate one-armed cap-cells. Leaves alternate. Inflorescence a thyrsoid panicle with corymbiform cymose branches bearing pedunculate heads or a single terminal head. Involucral bracts ca. 80 in ca, seven series, often with widely scarious margins and awns often black at tips; receptacles epaleaceous. Florets ca. 30 in a head; corollas whitish to purplish, basal tube long, narrowly funnelform distally, throat as long as the narrow glabrous lobes; anther bases plain, not tailed; apical appendage glabrous, with thin cell walls, sometimes weakly ornamented; style base with distinct annular node; branches with acicular sweeping hairs. Achenes 5 or 8-10-ribbed, setuliferous with setulae scarcely divided at tips, idioblasts present but not grouped, raphids elongate; pappus with copious barbellate setae, greenish, yellowish or tawny, rarely white, outer pappus short, squamiform. Chromosome number n = 9, 10 ( Jones 1979, 1982, Ayodele 1999).

Pollen lophate with ca. 32 lacunae, with five or more pores that seem to be rather asymmetrically distributed on the grains; the pores occur in lacunae that, in a few cases, are adjacent; margins of muri minutely echinate to psilate, without micropunctations, baculae closely spaced in single evenly spaced row under each murus, baculae in turn subtended by “rhizomate” structure that is weakly attached to the footlayer, the muri thus easily stripping away from the footlayer (Fig. 22 C ). The pollen of Polydora proves to have a lophate condition with well-defined lophae or muro bearing 4-5 spinules on each segment. The lophae are subtended by columellae in a single series not leaving an ogee-shaped gap in the middle.

Notable secondary metabolites: sesquiterpene lactone glaucolides/hirsutanolies ( Bohlmann and Jakupovic 1990, as Vernonia poskeana Vatke & Hildebr.), elemanolides, eudesmanolides, secoglaucolides ( Herz 1996, as Vernonia poskeana Vatke & Hildebr.

Polydora angustifolia is the species with which Steetz first introduced the use of pollen structure in the taxonomy of the Asteraceae (Steetz in Peters 1864). The generic name Crystalopollen was based on the lophate pattern of the pollen observed by Steetz.

Figures

Figure 20. Photographs of Parapolydora and Polydora: A-C Parapolydora fastigiata (Oliv. & Hiern in Oliv.) H. Rob. D-F Polydora poskeana (Vatke & Hildebrandt) H. Rob. See Appendix C for citation details.

Figure 22. Scanning electron micrographs of Polydora angustifolia (Steetz) H, Rob. A Intact grain with visible pore B Intact grain with 2 visible pores in adjacent lacunae C Grain with muri partially removed showing distorted inner surface and five pores, one pore on opposite surface visible through torn area. A from Brass 16090 B, C from Christensen & Patel 1457. Views from Robinson & Skvarla, PhytoKeys 2014.