10. Manihot Miller, Gard. Dict. Abr. ed. 4. vol. 2. 1754.
Cassava, yuca, manioc [From Brazilian vernacular name mani oca, wood spirit root, alluding to use] Cassava, yuca, manioc [From Brazilian vernacular name mani oca, wood spirit root, alluding to use]
W. John Hayden
Herbs, subshrubs, shrubs, or trees, perennial, unarmed, usually monoecious, rarely dioecious; hairs unbranched or absent; latex white. Leaves persistent or deciduous, alternate, simple [palmately compound]; stipules present, deciduous; petiole present [rudimentary], glands absent; stipels present at apex; blade usually palmately lobed, rarely unlobed, lobes undivided or secondarily lobed, margins entire, repand, or serrate, laminar glands absent; venation palmate (pinnate in lobes). Inflorescences bisexual (pistillate flowers proximal, staminate distal), terminal or axillary, racemes or panicles; glands subtending each bract 0. Pedicels present, pistillate often elongating in fruit. Staminate flowers: sepals 5, petaloid, 7–20 mm, valvate, connate 1/2 length; petals 0; nectary intrastaminal, cushion-shaped, lobed; stamens (6–8)–10, in 2 whorls, distinct; pistillode absent. Pistillate flowers: sepals 5, petaloid, distinct; petals 0; nectary annular, lobed or unlobed; pistil 3-carpellate; styles 3, connate basally, unbranched, flabellate, prominently papillate. Fruits capsules. Seeds globose to oblong; caruncle present. x = 9.
Species ca. 100 (6 in the flora): s United States, Mexico, Central America, South America.
Manihot is one of the most economically important members of Euphorbiaceae, primarily because of the starchy food-bearing roots of M. esculenta, now cultivated throughout the tropics. Also, M. glaziovii Müller Arg., from northeastern Brazil, was once an important source of Ceará rubber. Manihot appears to be most closely related to Cnidoscolus, a conclusion supported by morphological (G. L. Webster 1994) and DNA sequence data (K. Wurdack et al. 2005). Four species of sect. Parvibracteatae, as defined by D. J. Rogers and S. G. Appan (1973), barely extend across the borders of Arizona and Texas from Mexico. In addition, two species are naturalized in the southeastern United States.
Leaf blade lobe characters (length, outline) are best developed in the median and immediately adjacent lobes; lateral lobes are progressively smaller and tend to have simpler outlines with distance from the median lobe.
SELECTED REFERENCES Croizat, L. 1942. A study of Manihot in North America. J. Arnold Arbor. 23: 216–225. Rogers, D. J. 1963. Studies of Manihot esculenta Crantz and related species. Bull. Torrey Bot. Club 90: 43–54. Rogers, D. J. and S. G. Appan. 1973. Manihot, Manihotoides (Euphorbiaceae). In: Organization for Flora Neotropica. 1968+. Flora neotropica. 110+ nos. New York. No. 13. Webster, G. L. 1994. Synopsis of the genera and suprageneric taxa of Euphorbiaceae. Ann. Missouri Bot. Gard. 81: 33–144. Wurdack, K., P. Hoffman, and M. W. Chase. 2005. Molecular phylogenetic analysis of uniovulate Euphorbiaceae (Euphorbiaceae sensu stricto) using plastid rbcL and trnL-F DNA sequences. Amer. J. Bot. 92: 1397–1420.