Jatropha macrorhiza Benth.

  • Authority

    Dehgan, Bijan. 2012. . Fl. Neotrop. Monogr. 110: 1--274. (Published by NYBG Press)

  • Family

    Euphorbiaceae

  • Scientific Name

    Jatropha macrorhiza Benth.

  • Type

    Type. Mexico. Aguascalientes, Jul-Sep 1837, K. T. Hartweg 35 (lectotype, here designated: K; photos of of lectotype: F, MICH; isolectotypes: BM, G, GH, K, NY; syntype: Hartweg 31, P; photo of syntype: F).

  • Synonyms

    Jatropha macrorhiza var. septemfida Engelm., Jatropha arizonica I.M.Johnst.

  • Description

    Species Description - Perennial herbs, to 0.5 m tall. Stems: subterranean caudex, fleshy, to 12 cm in diam., stems and root scars round; cauline stems green, erect, herbaceous, and somewhat succulent, glabrous, often sparsely branched; latex clear; short shoots absent. Leaves: deciduous together with cauline shoots, lateral on stems; stipules persistent, filiform-divided, 4-10 mm; petioles 4.8-10-5 (-13.5) cm long and 1.5-1.8 (-2.8) mm in diam.; blades heteromorphic, cordate in outline, (3-)5-7(-9) lobes extending to middle, 11-16 x 9.3-11.2 cm, membranous, base cordate, margins coarsely dentate, apices acuminate, venation palmate with 5-7(-9) primary veins, glabrous on both surfaces except pubescent on veins of abaxial side. Inflorescences: terminal and subterminal, many-flowered cymes; peduncles 1.5-4.5 cm; bracts (6-)8-16 mm, margins serrate, glabrous; pedicels 2.5-4 mm. Staminate flowers: sepals lanceolate, 5-7 x 1-2 mm, distinct or connate to ½ of length, margins divided, apex acuminate, glabrous on both surfaces; corollas rotate-campanulate, light pink and often with white striations, petals 8-11.5 x 2.5-4.5 mm, distinct or connate ¼ of length, apex rounded, glabrous on both surfaces; stamens 8(-9), biseriate-diadelphous (5 + 3), filaments of outer series 3.5-6 mm, distinct, inner series 4.5-9 mm, connate to ½ of length. Pistillate flowers: like staminate but slightly larger; carpels 3; styles 3.5-4 mm, distinct or connate only at base. Capsules: spherical but distinctly 3-lobed, 1.2-1.3 cm in diam. Seeds: pale gray, ellipsoidal, 8-9 x 6-6.5 mm; caruncle prominent.

  • Discussion

    Local names and uses. Bahada, jicamilla, jirawilla, and ragged nettlespurge. Tumor-inhibiting properties have been identified in J. macrorhiza (Torrence et al., 1977). However, it also has toxic properties and, when digested, symptoms include dehydration and cardiovascular collapse as a result of haemorrhgic gastroenteritis, as well as central nervous system depression, (http:// www.inchem.org/documents/pims/plant/jmacro.htm).

    The annotation by Bentham on the type specimen [Hartweg 35 (K)] mentions Zacatecas as the collection locality but also notes Aguascalientes. Perhaps this should not be considered an inconsistency, because the Zacatecas-Aguascalientes area was a single state until 1835. According to Bentham (1839), Hartweg was sent to Mexico in 1836, at which time perhaps the status of the two states was not entirely settled. Irrespective of this historical detail, it is unclear in which of the two current states the collection was made. I have seen only one collection [McVaugh 16678 (MICH)] from Agua-calientes and none from Zacatecas. All other specimens were collected from Chihuahua and Sonora, the Mexican states adjacent to Arizona.

    Plants from the United States often have been called Jatropha macrorhiza var. septemfida Engelm., in reference to having 7 (as opposed to 5) leaf lobes or segments. However, leaf segment numbers vary from 3 to 9, even on the same plant and same shoot, so a distinct variety is not warranted. McVaugh (1945a) reported this species to have 10 stamens. I have not seen any life or herbarium specimens with 10 stamens, although two collections have 9 stamens. Bentham (1839) in the original protologue also reported 8 stamens. Jatropha macrorhiza is unusual in having a nyctonastic as as water-potential stress habit; flowers close at night and when the stem is cut. Hence, McVaugh’s inaccuracies with regard to flower characteristics were based on herbarium specimens with closed flowers.

    Jatropha macrorhiza was crossed with a number of species (Dehgan, 1984). These included: Jatropha macrorhiza x J. curcas [B. Dehgan B74.165 (DAV)]; Jatropha macrorhiza x J. integerrima [B. Dehgan B75.190 (DAV, NY)]; Jatropha macrorhiza x J. mo-rami [B. Dehgan B75.193 (DAV)]; Jatropha macrorhiza x J. capensis (L.f.) Sond. [B. Dehgan B 75.192 (DAV, NY)]. The last hybrid is of particular interest, because J. capensis is a South African endemic, and their ability to cross and produce some fertile seeds is indicative of affinity of the species on the two continents. The plants of J. macrorhiza used in these hybridization studies were collected in Arizona (Dehgan & Webster B74.016, B74.021).

  • Distribution

    Arizona, far eastern New Mexico, and northern Mexico in grassy brushlands, on hillsides and mesas, and in sandy or clay washes, at elevations of 1000-2500 m. A single collection from Presidio Co., Texas may be from cultivation or erroneously labeled: Trans-Pecos, Brite Ranch, near Valentine, 28 Jul 1938, L. C. Hinckley 1101 (NY, F). Flowering and fruiting primarily during spring and summer periods of active growth.

    Arizona United States of America North America| Aguascalientes Mexico North America| Chihuahua Mexico North America| Sonora Mexico North America| Florida United States of America North America| New Mexico United States of America North America| Mexico North America|