Flora of Barro Colorado Island

Acalypha macrostachya

Jacq., Hors. Schoenbr. 2:63, t. 245. 1797

Monoecious or dioecious shrub or small tree, 3-5 (8) m tall; stems often clustered, densely pubescent. Leaves alternate, simple; stipules paired, lanceolate, long-­acuminate, pilose, caducous leaving a scar; petioles 12-25 cm long, pilose; blades ± ovate, long-acuminate, truncate to cordate at base, 10-21 cm long, 7-15 cm wide, pilose especially on veins, crenate-serrate. Spikes axillary, usually unisexual, usually a few pistillate spikes alternat­ing with many staminate ones on apical part of stem, the staminate spikes usually 14-20 cm long, the pistillate spikes to 22 cm long in flower (to ca 30 cm long in fruit); petals and disk lacking; staminate flowers 4-lobed, ca 1 mm. or less wide; filaments fleshy, the thecae divergent; pollen ± tacky; pistillate flowers solitary, subtended by foliaceous bracts, the bracts 2.5-5 mm long (to 8 mm in fruit), their margins deeply toothed; styles 3, ca 1 cm long, red, slender, branched many times. Capsules tri­lobate, to 4.3 mm diam, hispid, explosively dehiscent; seeds 3, 1 per carpal, ellipsoid, ca 2 mm long. Croat 8602.

Occasional, in the forest, generally in areas of distur­bance along trails. Flowers principally from February to May, less frequently elsewhere in Panama during August and September. The fruits develop within about 6 weeks, the majority being dispersed during the late dry and early rainy seasons.

Although the stigmas are ideally suited to catching wind-dispersed pollen, the pollen is tacky and does not appear to be blown from the staminate flowers. However, the entire staminate flower is light and easily loosened and may be wind borne. Though capsules are explosively dispersed, the large bracts may act as receptacles for the dispersed seeds and thus serve as a wind ballast.

Southern Mexico to Peru, Bolivia, and Brazil. In Pan­ama, ranging about the same as A. diversifolia, but less abundant and preferring weedier habitats.

See Fig. 316.

Photos from STRI Digital Archive

  • Acalypha macrostachya flower plant
  • Acalypha macrostachya Inflorescence
  • Acalypha macrostachya Inflorescence
  • Acalypha macrostachya flower plant
  • Acalypha macrostachya flower plant
  • Acalypha macrostachya leaf
  • Acalypha macrostachya flower
  • Acalypha macrostachya
  • Acalypha macrostachya
  • Acalypha macrostachya