Acoraceae

Abstract

Acoraceae, in the order of Acorales, is a family of monocotyledonous flowering plants, with solitary genus, namely, Acorus Linn., comprising two species, distributed in temperate and subtropical Asia, North America, and tropical Asia. They are introduced and naturalized in Europe, New Guinea, and North America. Plants are perennial herbs, glabrous, and aromatic and often occur in marshes, shallow waters, or wetlands. Laticifers and raphides are absent, while aerenchyma are present. Rhizomes are creeping, much branched, and lacunose. Leaves are distichous, bases overlapping, unifacial, ensiform, and not differentiated into petiole and blade. Inflorescences are solitary, terminal, borne laterally on scape, and continuous shoot arising in axil of leaf preceding inflorescence. Spathe is much longer than spadix, erect, and persistent. Spadix is jutting out at an angle from peduncle, sessile, conoid, and cylindric. Flowers are bisexual, with perigone, densely arranged, bractless, and 3-merous. Tepals are six, in two whorls of three, free, thin, and arched. Stamens are six, in two whorls of three, free, filaments linear-oblong, and flattened. Anthers are introrse, thecae globose-ellipsoid, subopposite, dehiscing by longitudinal slit, and connective inconspicuous. Gynoecium (pistil) are obconic-cylindric, and only slightly exceeding tepals. Ovary are 2- or 3-locular. Ovules are several per locule, orthotropous, pendent on apical placenta, both integuments bearing trichomes with inner integuments longer than outer, forming micropyle, stigma minute, and subsessile. Fruit is a few-seeded berry, oblong-obovoid with thinly leathery pericarp, enclosed by tepals, whitish with brownish stigma remnant when fresh, soon drying to straw-brown, and 1–5(−9)-seeded. Seeds are oblong to ellipsoid. Testa is light brown, with small pits or smooth, and with long integumentary trichomes present at micropyle or absent. Embryos are axile, cylindric or conoid, and with perisperm and abundant endosperm. One species, Acorus gramineus Soland., is illustrated in this chapter.