The families of flowering plants

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L. Watson and M. J. Dallwitz

Rapateaceae Dum.

Habit and leaf form. Herbs (often coarse). Perennial; with a basal aggregation of leaves; mostly with simple stems, rhizomatous. Helophytic, or mesophytic. Leaves alternate; tristichous; flat to folded (usually V-shaped), or terete; petiolate (e.g.Saxofredericia), or subsessile; sheathing. Leaf sheaths not tubular; with free margins. Leaves simple. Lamina twisted through 90 degrees (usually), or neither inverted nor twisted through 90 degrees (?); entire; conspicuously asymmetric to not conspicuously asymmetric (the midvein commonly displaced to one side); commonly linear to lanceolate; parallel-veined.

General anatomy. Plants with silica bodies.

Leaf anatomy. The leaf lamina dorsiventral, or centric. Epidermis containing silica bodies (in the form of rounded druses). Stomata present; mainly confined to one surface (abaxial, neither sunken nor organized into regular files); paracytic (Dahlgren et al.1985). Guard-cells ‘grass type’ (Dahlgren et al. 1985). The mesophyll not containing mucilage cells; without calcium oxalate crystals. Foliar vessels mostly absent.

Axial (stem, wood) anatomy. Secondary thickening absent.

The vessel end-walls scalariform, or simple.

Root anatomy. Root xylem with vessels; vessel end-walls scalariform, or simple (mostly scalariform).

Reproductive type, pollination. Plants hermaphrodite. Floral nectaries absent (Cronquist 1981). Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in ‘spikelets’. Inflorescences scapiflorous (usually, the scape usually rather long), or not scapiflorous (in Maschalocephalus, where the scape is greatly reduced); axillary; each comprising a capitate to unilaterally racemose cluster of (1–)many pedunculate or sessile spikelets, borne on a short, compact inflorescence receptacle; with involucral bracts (usually, there being (1–)2 often large, basally broad, sometimes fused spathal leaves, rarely completely enclosing the infloresence); more or less pseudanthial; spatheate. Flowers (multi-) bracteate; regular to somewhat irregular; 3 merous; cyclic; pentacyclic. Perigone tube absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla; 6; 2 whorled; isomerous; sepaloid and petaloid; without spots (usually), or spotted (very rarely); different in the two whorls. Calyx 3; 1 whorled; polysepalous, or gamosepalous (chaffy, indurated at the base, sometimes basally connate); regular; imbricate. Corolla 3 (ephemeral, fragile); 1 whorled; polypetalous (rarely), or gamopetalous (usually tubular below); imbricate; regular; for the most part yellow, or red; plain, or with contrasting markings (sometimes with brown or violet spots).

Androecium 6. Androecial members free of the perianth, or adnate; free of one another, or coherent (the filaments often connate at the base); 2 whorled (3+3). Androecium exclusively of fertile stamens. Stamens 6; inserted when epipetalous, near the base of the corolla tube; diplostemonous; oppositisepalous; both alternating with and opposite the corolla members; alterniperianthial; filantherous (the filaments short, the anthers usually very long but shorter than the corolla). Anthers (sub-) basifixed; non-versatile; dehiscing via pores to dehiscing via short slits (by one, two or four openings); introrse; unilocular (occasionally), or bilocular; bisporangiate (when unilocular), or tetrasporangiate; shortly appendaged. The anther appendages apical (by short connective extension). Endothecium developing fibrous thickenings. The endothecial thickenings spiral. Microsporogenesis probably simultaneous. The initial microspore tetrads tetrahedral. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 1 aperturate, or 2 aperturate; sulcate, or sulculate, or zoniaperturate; probably 2-celled.

Gynoecium 3 carpelled. Carpels isomerous with the perianth. The pistil 1 celled, or 3 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 3 locular (but the partitions sometimes incomplete near the top, and only one of the locules fertile in Spathanthus). Gynoecium stylate. Styles 1; apical. Stigmas 1; simple. Placentation axile, or basal to axile (when few-ovuled). Ovules 1–2 per locule, or 5–50 per locule (to ‘many’); ascending; anatropous; crassinucellate. Embryo-sac development Polygonum-type. Endosperm formation nuclear.

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Seeds copiously endospermic. Endosperm not oily (mealy, starchy). Seeds winged, or wingless. Seeds with starch. Embryo rudimentary at the time of seed release (small, lenticular, situated at the micropylar end). Testa without phytomelan.

Seedling. Coleoptile absent.

Physiology, phytochemistry. Acumulated starch other than exclusively ‘pteridophyte type’. Aluminium accumulation demonstrated (the most notable of Monocots in this respect).

Geography, cytology. Paleotropical (Maschalocephalus only), or Neotropical. Tropical. Eastern tropical South America, West tropical Africa. 2n = 22 in Maschalocephalus.

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Commeliniflorae; Commelinales. APG 3 core angiosperms; Superorder Lilianae; commelinid Monocot; Order Poales.

Species 80. Genera 17; Amphiphyllum, Cephalostemon, Duckea, Epidryos, Guacamaya, Kunhardtia, Marahuacaea, Maschalocephalus, Monotrema, Phelpsiella, Potarophytum, Rapatea, Saxofridericia, Schoenocephalum, Spathanthus, Stegolepis, Windsorina.


This description is offered for casual browsing only. We strongly advise against extracting comparative information from it. This is much more easily achieved using 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).

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 2013. http://delta-intkey.com’.

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