Manihot Manihotoides (Euphorbiaceae) - CNCFlora

Systematic Position of the Genus 19
SYSTEMATIC POSITION OF THE GENUS
The 12th edition of Syllabus der Pflanzenfamilien (Melchior, 1964) places the genus
Manihot in a separate tribe, Manihotae, primarily on the basis of the single perianth whorl
in the species. We concur in this placement, because it removes some of the confusion
caused by Pax's (1910) inclusion of the genus in the tribe Adrianeae along with several
other genera of little relation to Manihot. Linnaeus' placement of the species Manihot
esculenta in the genus Jatropha has caused considerable nomenclatorial confusion, though
little confusion among those who have studied the two genera in any detail. The usual
double perianth whorls of Jatropha clearly distinguish the two genera, and this distinction
has been reflected in more recent placement of Manihot and Jatropha in different tribes.
Miller and Webster (1962), discussing the differences which clearly separate the two
genera Jatropha and Cnidosculus, raise the possibility of a close relation between the
latter genus and Manihot. They suggest that because both Manihot and Cnidosculus have
a single floral envelope, and both share a common base chromosome number (X = 9), that
the genus Cnidosculus should be given a different assignment in the Crotonoideae, but
state that it would be premature, with present knowledge, to make a definite placement
other than in the Jatrophinae. We concur that it is premature, and that careful
comparative studies need to be made over the whole suprageneric classification before
good decisions can be made. Clearly such a study is beyond the scope of this monograph.
1. MANIHOT P. Miller, The Gardener's Dictionary Vol. II, London, 1754, 4th Ed;
Adanson, Fam. II. 356. 1763; Crantz, Inst. Rei Herb. I. 658. 1766; Pohl, P1. Bras. Ic.
et Descr. 1. 17-56. 1827; Muell.-Arg. in DC. Prodr. 15(2): 1057-1075. 1866; in
Martius Fl. Bras. 11(2): 438-486. 1874; Pax in Engler, Pflanzenr. IV. 147(Heft 44):
21-111. 1910; Standley, Contr. U.S. Nat. Herb. 23: 1923; Pax & Hoffmann in
Engler, Pflanzenr. IV. 147(Heft 85): 194-197. 1924; Croizat, Jour. Arnold Arb. 23:
216-225. 1942.
Jatropha L. Sp. PI. ed. 1. 1007. 1753 pro parte.
Janipha H.B.K., Nov. Gen. et Spec. II. 84. t. 109. 1817.
Mandioca Link, Handb. II. 436. 1831.
Subshrubs, shrubs, trees or clambering vines. Latex usually, but not universally,
produced in varying quantities. Plants typically producing a cyanogenetic glucoside,
varying in concentrations from a few parts per million to ca 500 ppm.
Roots tuberous or slender, the former condition predominant, frequently with large
concentrations of stored starch; root epidermis smooth or roughened, peeling, frequently
with lenticels clearly defined; subepidermis white, or frequently with varying intensities
of red or yellow; phelloderm well-developed ca 0.2-0.3 cm thick; tuberous rooted species
with cortex of white, cream or yellow parenchymatous tissues for starch storage; usually
with a well-defined central vascular strand.
Stems nearly acaulescent to caulescent; several of the suffruticose species with
semiherbaceous stems dying back to a root crown; stem diameters to 30 cm at breast
height; the internodes of the nearly acaulescent species telescoped; nodes of at least one
species prominently enlarged; stems variously light gray, dark brown, yellowish to
reddish; bark of the tree species generally smooth, infrequently roughened or peeling;
branching generally dichotomous or trichotomous, the branching point determined by
the presence of a terminal inflorescence; young stems with or without varying degrees of
pubescence, green to dark red.