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The families of flowering plants

L. Watson and M. J. Dallwitz

Xanthophyllaceae (Chodat) Gagnep.

~ Polygalaceae.

Habit and leaf form. Small trees. 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. Hairs present; eglandular; unicellular and multicellular. Unicellular hairs simple. Multicellular hairs uniseriate. The mesophyll without crystals (? at least, not recorded).

Axial (stem, wood) anatomy. Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral (?). Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. The axial xylem with vessels.

The wood diffuse porous. The vessels medium to large; solitary. The vessel end-walls simple. The axial xylem without fibre tracheids; with libriform fibres. The parenchyma apotracheal (sic: banded — see Metcalfe and Chalk 1965). ‘Included’ phloem absent. The wood not storied.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in panicles. The ultimate inflorescence units 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. Floral receptacle with neither androphore nor gynophore. 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; not becoming inverted during development; 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; 1 seeded. Seeds non-endospermic.

Physiology, phytochemistry. 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.

General remarks. Differing clearly from Polygalaceae in the unilocular gynoecium with 2–16 ovules and the dorsifixed anthers, in wood anatomy, and perhaps also in the strong tendency to accumulate aluminium.

Illustrations. • Xanthopyllum angustifolium: Wight’s Illustrations of Indian Botany 1 (1840).

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: 19th October 2016.’.