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The families of flowering plants

L. Watson and M.J. Dallwitz

Dialypetalanthaceae Rizz. & Occh.

~ Rubiaceae.

Habit and leaf form. Trees. Plants green and photosynthesizing. Leaves opposite; simple. Lamina entire; pinnately veined; cross-venulate. Leaves stipulate. Stipules intrapetiolar; concrescent (large, ‘laterally connate towards the base in pairs’: Cronquist 1981). Lamina margins entire.

Axial (stem, wood) anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring.

The vessel end-walls simple. The parenchyma scanty apotracheal (or virtually none). ‘Included’ phloem absent.

Reproductive type, pollination. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the disk.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. The ultimate inflorescence units cymose. Inflorescences terminal; cymose panicles or thyrses. Flowers bracteate (the bracts resembling the stipules, but smaller); (bi-) bracteolate; showy; fragrant; regular; cyclic; polycyclic. Free hypanthium absent.

Perianth with distinct calyx and corolla; 8; 4 whorled; isomerous. Calyx 4; 2 whorled (decussately 2+2); polysepalous; regular; persistent. Corolla 4; 2 whorled (2+2); polypetalous; regular; white.

Androecium (16–)18(–25). Androecial members free of the perianth; all equal; coherent; 1 adelphous (basally connate into a tube); 2 whorled. Androecium exclusively of fertile stamens. Stamens (16–)18(–25); polystemonous; erect in bud; shortly filantherous. Anthers basifixed; dehiscing via pores (apically); introrse; bilocular (the locules separated on the triquetrous connective); tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium 2 carpelled. Carpels isomerous with the perianth. The pistil 2 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; inferior. Ovary 2 locular. Epigynous disk present (in the form of a fringe atop the ovary). Gynoecium stylate. Styles 1; apical; elongate. Stigmas 1–2; shortly 2 lobed. Placentation axile. Ovules 30–50 per locule (‘many’); anatropous; bitegmic.

Fruit non-fleshy; dehiscent; a capsule. Capsules valvular (septifragal according to Cronquist). Fruit 50–100 seeded (‘many’). Seeds thinly endospermic. Endosperm oily. Seeds slender, fusiform, somewhat sigmoid. Embryo well differentiated. Cotyledons 2 (short). Embryo straight.

Physiology, phytochemistry. Not cyanogenic. Iridoids not detected.

Geography, cytology. Neotropical. Tropical. Eastern Brazil.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli (?). Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Rosidae; Rosales. APG III core angiosperms; core eudicot; Superorder Asteranae; lamiid. APG IV Order Gentianales (as a synonym of Rubiaceae).

Species 1 (Dialypetalanthus fuscescens). Genera 1; only genus, Dialypetalanthus.

General remarks. Differing from the sensu stricto description compiled for Rubiaceae (q.v.) in 15 conspicuous floral and fruit characters.

Illustrations. • Dialypetalanthus fuscescens: Kuhlmann, Arch. Jard. Bot. Rio de Janeiro 4 (1925). • Dialypetalanthus fuscescens (Hutchinson).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.