Manihot walkerae Croizat

  • Authority

    Rogers, David J. & Appan, S. G. 1973. Manibot, Manihotoides (Euphorbiaceae). Fl. Neotrop. Monogr. 13: 1-272. 1 chart. (Published by NYBG Press)

  • Family

    Euphorbiaceae

  • Scientific Name

    Manihot walkerae Croizat

  • Type

    TYPE. Walker (Parks, H. B.) s n: USA, Texas: Mission, 1940 (holotype, A; isotypes, A-2).

  • Description

    Description - Decumbent shrubs, ca 0.5 m tall, profusely branching, branches slender, prostrate, long, weak. Roots prominently enlarged, carrot shaped, ca 10.0 cm long; epidermis very dark brown, rough with bands of laterally oriented corky strips; cortex white with strong smell of HCN; tuberous roots reported to possess adventitious buds (used as propagating material, Walker 1003). Young stems glabrous, greenish brown; mature stems glabrous, grayish brown. Leaves alternate; stipules setaceous, deciduous, glabrous; petioles slender, usually 7.0-10.0 cm long, glabrous, terete, ventral surface dark dull red, dorsal surface greenish; lamina peltate, over 0.5 cm wide at the region between the petiole attachment point and the lamina margin at the base of the leaf, ventral lamina deep green, dorsal lamina markedly glaucescent, abaxial surface wax pattern smooth; venation craspedodromous; palmately 5 lobed, 3 major and 2 smaller lobes; median lobes ovate-ellipsoid to more or less parabolic, pandurate, rarely entire-lobed, usually 5.0-10.0 cm long, the basal lobule apex abruptly dilated, cuspidate, terminating in a spine-like point; lamina margin above and below the basal lobule incised, often deeply, into lobulets which also terminate in spine-like extensions, apex acute to acuminate; the sinuses on either side of the median lobe with a characteristically flat base forming an almost 45 angle to the median lobe midrib; lowest lobes about half as long as median lobes, apex cuspidate. Inflorescence a monoecious, axillary, subspicate, raceme, 5.0-10.0 cm long, all parts glabrous; bracteoles setaceous, less than 0.3 cm long, glabrous, margin serrate; bractlets setaceous, glabrous. Pistillate flowers restricted to the very base of the inflorescence, borne on ca 1.5 cm long pedicels (which appear attached directly to stem); tepals ca 1.1 cm long, light purplish streaked externally, cleft to the base into 5 oblong-lanceolate lobes; disc fleshy, entire, with several staminodes; pistil ca 0.6 cm long, ovary subglobose, the trifid stigma well lobed and lobulate. Staminate flowers almost tubular, distinctly constricted in the middle, tepals ca 1.2 cm long, light purplish streaked externally, cleft 1/3 of the way down into 5 lobes, the lobes oblong, tapering, not prominently reflexed at anthesis; disc fleshy, 5 lobed; stamens 6-10 (6, 7, and 8 observed, 10 reported in original description), superior whorl ca 0.9 cm long, inferior whorl ca 0.7 cm long, filaments and anthers cream colored. Fruit pedicels slightly curved downwards ca 1.5 cm long, pistillate pedicels attached to the very base of the inflorescence; capsules almost globular, ca 1.0 cm long from base to apex, surface sparingly but manifestly verrucose and rugose, ribs not prominent; fruit dehiscence septicidal. Seeds rotund, ca 0.8 cm long; caruncle very prominent, large in comparison to seed size, ca 0.2 cm long and ca 0.4 cm broad, cream colored, slightly cleft and 2 lipped in front.

  • Discussion

    This distinct species may be very close to extinction in the localities along the Rio Grande in Texas and adjoining Mexico due to intensive cultivation in this area. The illustrations, and much of the detailed description of Manihot walkerae were taken from the small but vigorous colony established on the south side of the Department of Botany building at the University of Texas, Austin, Texas.

  • Distribution

    USA: Texas; Mexico: Tamaulipas.

    United States of America North America| Texas United States of America North America| Mexico North America| Tamaulipas Mexico North America|