Valantia muralis L.  

An annual with erect, ascending or decumbent, much-branched stems up to 20 cm long. Stems four-angled, hairless on the lower parts and densely hairy on the upper parts. Leaves 0.5 to 7 mm long, elliptical, lanceolate or obovate, hairless, in whorls of 4. Flowers greenish-yellow, about 0.6 mm across, in threes, in dense axillary clusters. The middle flower of the three hermaphrodite, with four lobes; the lateral ones male, with three lobes. Peduncles and pedicels curve downwards, thicken and harden, enclosing the fruit, forming a structure between 2 and 3 mm long, with 2 to 4 horns. Fruiting structure with a prominent, erect horn-like appendage with fringed tip on the back. Fruit generally with 1 mericarp.