Eriocaulaceae

Abstract

Medium-sized perennials, hapaxanthic perennials or annual herbs, usually rosulate, often tufted, rarely caulescent, with horizontal or erect rhizomes. Indumentum of multicellular uniseriate and sometimes glandular hairs, terminal cell simple or bibranched (malpighiaceaous hairs). Leaves usually spirally arranged, rarely distichous, in some species distichous in the vegetative parts and spirally in the inflorescence or vice versa. Inflorescences forming single headlike indeterminate spikes (here called heads) on thin peduncles, or composed of many (up to 1000) such heads. Peduncles with a closed sheath at the base. Heads composed of 10 to more than 1000 unisexual flowers. Heads subtended by an involucrum (involucral bracts) different in size and shape from bracts subtending flowers; the two types connected by intermediates. Inner involucral bracts petaloid and capable of hygroscopic movements in Paepalanthus subgen. Xeractis and Syngonanthus sect. Eulepis. Flowers generally unisexual (hermaphrodite only in Rondonantus flabelliformis, Syngonanthus amazonicus and few related species), mostly monoecious, rarely and then not constantly dioecious, heterochlamydeous, actinomorphic or slightly zygomorphic, trimerous or dimerous, nearly always isomerous, rarely heteromerous (2- and 3-merous). Sepal whorl and bracts white, brownish, yellow, or dark green to black. Petal whorl generally colorless or white, often hyaline, sometimes yellow or brown when dried, rarely (Syngonanthus anthemidiflorus) petals and gynoecium yellow. Stamens usually 3 or 2, oppositipetalous, or 6 or 4 in 2 whorls (only Eriocaulon, Mesanthemum), Syngonanthus amazonicus with a single stamen. Anthers introrse, basifixed or dorsifixed, 2-thecate 4-sporangiate, in some species 2-thecate 2-sporangiate by facial reduction (Lachnocaulon, Blastocaulon, some spp. of Paepalanthus). Ovary 3- or 2-locular, each locule with a single atropous pendulous ovule. Fruit a dorsicidal loculicidal capsule. Seed coat longitudinally striated or “hairy” by residuals of anticlinal walls of the inner layer of the outer integument. Embryo small, bell-shaped, poorly differentiated, at the micropylar end laterally attached to the starchy endosperm.