Family Mayacaceae

Mayacaceae Kunth

Habit and leaf form. Creeping herbs (with a Lycopodium-like habit). With neither basal nor terminal aggregations of leaves. Stem growth conspicuously sympodial. Hydrophytic to helophytic; rooted. Leaves submerged to emergent. Leaves small; alternate; spiral (in high phyllotaxies); imbricate; sessile; non-sheathing; simple. Lamina entire, or dissected (then apically bifid only); linear (or filiform), or lanceolate; one-veined. Lamina margins entire.

General anatomy. Plants without silica bodies. Accumulated starch exclusively ‘pteridophyte type’.

Leaf anatomy. Stomata present; paracytic. Hairs absent (the plants glabrous save for ephemeral hairs in the leaf axils).

Lamina without secretory cavities (but with longitudinal air channels). The mesophyll not containing mucilage cells; without calcium oxalate crystals. Vessels present (?), or absent (with ‘vessel tracheids’).

Stem anatomy. Secondary thickening absent (typically with three vascular bundles, and an aerenchymatous cortex separated from the narrow central cylinder by an endodermis). Xylem with vessels. Vessel end-walls scalariform, or reticulately perforated.

Root anatomy. Root xylem with vessels; vessel end-walls reticulately perforated and scalariform.

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries absent.

Inflorescence, floral, fruit and seed morphology. Flowers solitary; terminal (but simulating lateral by sympodial growth of the shoots); bracteate (the bracts membranous); small (aerial); regular; 3 merous; cyclic; tetracyclic. Perigone tube absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla; 6; free; 2 whorled; isomerous; different in the two whorls. Calyx 3; 1 whorled; polysepalous; regular; imbricate, or valvate (‘subvalvate’). Corolla 1; 1 whorled; polypetalous; imbricate; regular; pale pink to purple (rose), or white. Petals shortly clawed; entire.

Androecium 3. Androecial members free of the perianth; all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 3; isomerous with the perianth; oppositisepalous; alternating with the corolla members; alterniperianthial (representing the outer whorl); filantherous (the filaments slender, glabrous). Anthers basifixed; non-versatile; dehiscing via pores to dehiscing via short slits (apically); bilocular (occasionally), or four locular; tetrasporangiate; appendaged (sometimes). The anther appendages when present, apical (the dehiscence being sometimes at the end of a tubular appendage). Endothecium not developing fibrous thickenings. Microsporogenesis successive. The initial microspore tetrads isobilateral and decussate. Anther wall initially with more than one middle layer; of the ‘basic’ type. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 1 aperturate; sulcate; finely reticulate; 2-celled.

Gynoecium 3 carpelled (the carpels alternating with the stamens). The pistil 1 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 1 locular; sessile. Gynoecium stylate. Styles 1; attenuate from the ovary; apical. Stylar canal present. Stigmas 1, or 3; when single, 1 lobed, or 3 lobed (capitate to trifid). Placentation parietal. Ovules in the single cavity 25–100 (‘many’); horizontal, or ascending; mainly biseriate; orthotropous; bitegmic; thinly crassinucellate, or tenuinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Synergids pear-shaped. Hypostase present (tanniniferous). Endosperm formation nuclear. Embryogeny onagrad.

Fruit non-fleshy; dehiscent; a capsule. Capsules three valvular (dehiscing midway between the placentae, i.e. each valve with a median placenta). Dispersal probably by water, floating via the air-filled exotesta. Seeds endospermic. Endosperm not oily (mealy, starchy and proteinaceous). Seeds with starch. Embryo rudimentary at the time of seed release. Embryo small, discoid-unipapillate, forming an apical cap on the endosperm at the micropylar end. Testa operculate (with a dorsal ‘embryostega’, cf. Commelinaceae, according to several sources), or non-operculate (Hamann 1961, who treats other reports as erroneous, suggesting that micropylar tissue merely disintegrates); without phytomelan.

Physiology, biochemistry. Not cyanogenic. Proanthocyanidins absent. Flavonols present; quercetin. Ellagic acid absent.

Geography, cytology. Holarctic, Paleotropical, and Neotropical. Sub-tropical to tropical. Southeast U.S.A., Central and tropical South America, tropical Southwest Africa.

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

Species 10. Genera 1; only genus, Mayaca.

Illustrations.
• Technical details: Mayaca (Lindley).