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Cephalanthus belongs to Rubiaceae tribe Naucleeae, and is characterized as shrubs to a small trees, mainly from the lowlands, with verticillate leaves. We hypothesized that the foliar morphoanatomy of Cephalanthus species provides characters informative to our taxonomic study, and that their leaves present adaptations to waterlogged habitats. To test these hypotheses our aims were to describe the macro- and micromorphology and anatomy of leaves in all Cephalanthus species. We describe and characterize leaf disposition, shape, size of blade and petiole, characteristics of the epidermis and indumenta, including the micromorphology of the cuticle and stomata, and the types of leaf domatia, if present. The anatomy of the petiole and leaf blade was also analyzed, including the mesophyll, vascular systems, ontogeny of the stomata, presence and typification of oxalate of calcium crystals, and their distribution in the foliar tissues. Uniformity in the morphoanatomical characters allows us to define the genus Cephalanthus, but inside this uniformity we can also differentiate between the species by means of a dichotomous key. The presence of domatia in pockets in C. occidentalis, in contrast to the tuft of hairs in C. salicifolius and C. tetrandrus, shed light on the taxonomic delimitation of the former because historically they were considered a single species. Cephalanthus species show variability in micromorphological characters, but have a strong uniformity in anatomical organization. The leaves of Cephalanthus show adaptations to seasonal environments; some are typical hydromorphic traits while other reflect adaptations to their heliophilic habitat and tolerance to dry periods. Fil: Romero, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina Fil: Salas, Roberto Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina Fil: González, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina

This paper is the first embryological report on the genus Cephalanthus L. and contributes to future studies in other genera in the tribe Naucleeae. The development of the anther wall in Cephalanthus glabratus (Spreng.) K. Schum. corresponds to the dicot type and microsporogenesis is simultaneous. The young wall of the anther has four layers: epidermis, endothecium, one middle layer and the secretory tapetum. The tissue of the septum has idioblasts with crystalline sand. In the wall of the mature anther, only the endothecium and remnants of epidermal cells were preserved. The occurrence and morphology of orbicules were observed in the mature anthers of all three species of Cephalanthus with scanning electron microscopy. The orbicules have taxonomic value at species level, since these structures allow us to distinguish between the species analyzed. The presence of a protruding oncus was observed for the first time in Cephalanthus in non-acetolyzed pollen grains. According to our observations, this structure is not affected by the state of anther dehiscence in Cephalanthus glabratus, because the oncus is visible and prominent in the mature pollen grains in both indehiscent and dehiscent anthers. Fil: Romero, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina Fil: Salas, Roberto Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura; Argentina Fil: González, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina

Rubiaceae are one of the largest families of plants, with ∼13,000 species. In this study, we have estimated the phylogeny for 534 Rubiaceae taxa from 329 genera with up to five different chloroplast regions by Bayesian analysis. It resulted in a highly resolved tree with many strongly supported nodes. There is strong support for the three subfamilies (Cinchonoideae, Ixoroideae, Rubioideae) and most of the 44 included tribes. A scaled‐down data set of 173 Rubiaceae taxa was used with a Bayesian approach to estimate divergence times for clades classified as tribes and subfamilies. Four fossils were used as minimum age priors, one inside each subfamily and one for Rubiaceae as a whole (Faramea‐type pollen, Scyphiphora pollen, Cephalanthus pusillus fruits, and Paleorubiaceophyllum eocenicum leaves). The estimated lineage (stem) divergence time for Rubiaceae is 90.4 Ma. The estimated lineage divergence times for the subfamilies are 84.4 (86.6) Ma for Rubioideae, 73.1 Ma for Ixoroideae, and 73.1 Ma for Cinchono...

This study describes floral morphology and phenology, self-incompatibility, and pollen tube growth rates in self- and cross-pollinations of C. occidentalis

Cephalanthus occidentalis Linnaeus, Species Plantarum 1: 95. 1753. "Habitat in America septentrionali." RCN: 793. Lectotype (Reveal in Jarvis & al., Regnum Veg. 127: 31. 1993): Herb. Linn. No. 118.1 (LINN). Generitype of Cephalanthus Linnaeus (vide Merrill in J. Wash. Acad. Sci. 5: 532. 1915; Hitchcock, Prop. Brit. Bot.: 123. 1929). Current name: Cephalanthus occidentalis . L. (Rubiaceae). Note: Ridsdale (in Blumea 23: 180. 1976) indicated 118.1 and 118.2 (LINN) as types but as the two sheets do not appear to be a single gathering, Art. 9.15 does not apply and Ridsdale’s statement does not constitute a valid typification., Published as part of Jarvis, Charlie, 2007, Chapter 7: Linnaean Plant Names and their Types (part C), pp. 370-473 in Order out of Chaos. Linnaean Plant Types and their Types, London :Linnaean Society of London in association with the Natural History Museum on page 403, DOI: 10.5281/zenodo.291971

We have isolated from Cephalanthus spathelliferus (Rubiaceae) five compounds: umbelliferone, skimmin, 7,4′-dimethylkaempferol,7,4′-dimethylaromadendrin and its 5-glucoside. The latter two are new compounds.

Cephalanthus occidentalis, spec. nov. 2. Cephalanthus foliis oppositis ternisque. Gron. virg.15. Cephalanthus foliis ternis. Hort. cliff. 73. Roy. lugdb. 187. Scabiosa dendroides americana, ternis foliis caulem ambientibus, floribus ochroleucis. Pluk. alm. 336. t.77. f.4. Habitat in America septentrionali. ��� Capsulae nullae. Semina solitaria, longa pyramidata: basi attenuata, angulata, lanuginosa; unilocularia. Receptaculum commune globosum, villosum., Published as part of Linnaeus, Carolus, 1753, Species plantarum: exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas, Stockholm :Laurentius Salvius on page 95, DOI: 10.5281/zenodo.3931989

Nerium salicinum Vahl, Symb. Bot. 2:45 (1791). Type: N. Yemen, Hadie, Mar. 1763, Forsskal 236 (C-1 sheet, syntype leaves only, IDC 2200 microfiche 70:111.3, 4); 237 (C-1 sheet, syntype leaves only, IDC 2200 microfiche 70:111.5, 6). Nauclea microcephala Delile, Cent. Pl. Mero&: 67 (1826). Type: Sudan, Cailliaud (MPU). Adina microcephala (Delile) Hiern in Fl. Trop. Afr. 3:40 (1877); Brown & Massey, Fl. Sudan :257 (1929); Schwartz, Fl. Trop. Arab. :262 (Mitteil. Inst. allge. Bot. Hamburg :10) (1939); Aubreville, Fl. For. Soud.-Guin. :474 (1950); Andrews, Fl. P1l. A-E. Sudan 2:423, fig. 156 (1952); Dale & Greenway, Kenya Trees and Shrubs :424 (1961); White, For. Fl. N. Rhod. :398 (1962); Hepper, Fl. W. Trop. Afr., ed. 2, 2:163 (1963); Keay, Onochie & Stanfield, Nigerian Trees 2:398 (1964); Cufodontis in Bull. Jard. Bot. Brux. 35:998 (1965); Wickens, Fl. Jebel Marra :129 (1976). Breonadia microcephala (Delile) Ridsdale in Blumea 22:549 (1975) and 24:362 (1978). Nauclea verticillata Baill. in Adansonia 12:284 (1879). Lectotype: Madagascar, Boivin s.n. (P). Cephalanthus spathelliferus Baker in Journ. Bot. 20:137 (1882). Type: Madagascar, Baron 86 (K). Adina spathel/ifera Oliv. in Hook. Ic. Pl.:t.2386 (note in text) (1895). A. galpinii Oliv. in Hook. Ic. Pl.:t.2386 (1895). Type: Swaziland, Galpin 1213 (K). A. lasiantha K. Schum. in Engler, Pflanzenw. Ost-Afr. C:261 (1895). Type: Malawi, Buchanan 6 (Bt).