Family Xanthophyllaceae

Xanthophyllaceae (Chodat) Gagnep.

~ Polygalaceae

Habit and leaf form. Small trees; non-laticiferous and without coloured juice. Leaves evergreen; alternate; leathery; not gland-dotted; simple. Lamina entire; cross-venulate (usually with the veinlets terminated by enlarged tracheary ideoblasts). Leaves exstipulate. Stipules probably represented by crateriform glands.

Leaf anatomy. Stomata present; anisocytic, or paracytic.

Stem anatomy. Nodes unilacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with vessels. Vessel end-walls simple. Wood parenchyma apotracheal (sic: banded — see Metcalfe and Chalk 1965).

Reproductive type, pollination. Fertile flowers hermaphrodite. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in panicles. The ultimate inflorescence unit cymose, or racemose. Inflorescences terminal, or axillary; racemelike with sessile dichasial clusters, or mixed panicles. Flowers very irregular; zygomorphic. The floral irregularity involving the perianth and involving the androecium. Flowers ‘pseudo-papilionaceous’, or neither papilionaceous nor pseudo-papilionaceous; cyclic. Free hypanthium absent. Hypogynous disk present; intrastaminal; annular.

Perianth with distinct calyx and corolla; (9–)10; 2 whorled. Calyx 5; 1 whorled; polysepalous; imbricate (the two inner members longer than the three outer); with the median member posterior. Corolla 4–5; 1 whorled; polypetalous; imbricate (unequal, the lowermost member internal and folded to form an often hairy keel). Petals clawed, or sessile.

Androecium 8. Androecial members free of the perianth, or adnate (then adnate to the petal claws); free of one another (not forming a tube). Androecium exclusively of fertile stamens. Stamens 8; more or less diplostemonous; both alternating with and opposite the corolla members; filantherous (the filaments more or less inflated and pubescent below). Anthers more or less dorsifixed; dehiscing via longitudinal slits; introrse; tetrasporangiate. Pollen grains aperturate; 7–30 aperturate (?); poly- colporate.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary unilocular; 1 locular. Gynoecium median. Ovary stipitate. Gynoecium stylate. Styles 1; apical. Stigmas 1; 2 lobed. Placentation parietal (with two placentas). Ovules in the single cavity 2–16; anatropous.

Fruit fleshy (-fibrous), or non-fleshy; indehiscent; without fleshy investment; 1 seeded. Seeds non-endospermic.

Physiology, biochemistry. Saponins/sapogenins present. Aluminium accumulation demonstrated (often, the leaves then yellow-green on drying).

Geography, cytology. Paleotropical. Tropical. Indomalayan region.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Polygalales. Cronquist’s Subclass Rosidae; Polygalales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Fabales (as a synonym of Polygalaceae).

Species 60. Genera 1; only genus, Xanthophyllum.