Family Dialypetalanthaceae

Dialypetalanthaceae Rizz. & Occh.

~ Rubiaceae

Habit and leaf form. Trees. 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.

Stem anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Vessel end-walls simple. Wood parenchyma scanty apotracheal (or virtually none).

Reproductive type, pollination. Unisexual flowers absent. 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 unit 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, biochemistry. 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 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Rosales (as a synonym of Rubiaceae).

Species 1. Genera 1; only genus, Dialypetalanthus.