18. Microstachys A. Jussieu, Euphorb. Gen. 48. 1824.
[Greek mikros, small, and stachys, spike, alluding to inflorescence] [Greek mikros, small, and stachys, spike, alluding to inflorescence]
Kenneth J. Wurdack
Herbs [shrubs], annual [perennial], monoecious; hairs unbranched [branched]; latex white. Leaves alternate, simple; stipules present, persistent; petiole present, glands absent; blade unlobed, margins serrulate [entire], laminar glands abaxial, at base [absent]; venation pinnate. Inflorescences appearing unisexual (pistillate and staminate portions usually shortly separated on stem), terminal, leaf-opposed, or axillary, racemelike thyrses; glands subtending each bract  2. Pedicels present, often rudimentary. Staminate flowers: sepals 3, imbricate, distinct [connate basally]; petals 0; nectary absent; stamens 3, distinct; pistillode absent. Pistillate flowers: sepals 3, distinct; petals 0; nectary absent; pistil 3-carpellate; styles [0 or]3, connate basally, unbranched. Fruits capsules, base not persisting. Seeds oblong, ends truncate [elliptic]; outer seed coat dry; caruncle present [absent].
Species ca. 15 (1 in the flora): introduced; Mexico, West Indies, Central America, South America, Asia, Africa, Australia; tropical and subtropical regions.
Microstachys is distinct based on morphology and molecular phylogenetic evidence (H.-J. Esser 1998; K. Wurdack et al. 2005), although species have been included historically in Sebastiania. The inflorescence architecture characteristic of Microstachys is unusual: the pistillate and staminate parts are usually shortly separated along the main stem, appearing as two separate partial inflorescences at consecutive nodes, the pistillate one proximal and supra-axillary, and the staminate distal and leaf opposed. The genus is known primarily from the New World with a few species found in Africa, Asia, and Australia.