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Annual or perennial, prostrate or decumbent herbs or subshrubs. Leaves simple, opposite, entire, with short often wing-like petiole. Inflorescence an axillary or terminal cluster or head or short spike. Flowers usually bisexual, subtended by bracts and bracteoles. Perianth segments 5, unequal, sepaline or hyaline. Stamens 2-5, inserted, filaments short, connate into a short cup with or without interpassed staminodes, anther 1-celled. Ovary ovoid or orbicular, 1-celled, ovule 1, stigma capitellate (rarely bifid). Fruit an indehiscent utricle, enclosed by the perianth. Seeds often lenticular.


Key to the species

Serial Key Reference
1a. Heads long-peduncled A. philoxeroides
1b. Heads sessile 2
2a. Tepals all similar in form, subequal or at most the inner slightly shorter than the outer 3
2b. Tepals very dissimilar both in length and form A. pungens
3a. Tepals prominently 3-nerved in the lower half, hairy on back 4
3b. Tepals 1-nerved with prominent mid-rib, glabrous A. sessilis
4a. Prostrate, mat-forming herbs; pseudostaminodes much shorter than the stamens A. paronychioides
4b. Erect or ascending, bushy herbs; pseudostaminodes as long as the stamens A. ficoidea