Mimosa debilis var. amnis-mortium

  • Title

    Mimosa debilis var. amnis-mortium

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Mimosa debilis var. amnis-mortium Barneby

  • Description

    326e. Mimosa debilis Humboldt & Bonpland ex Willdenow var. amnis-mortium Barneby, var. nov., a caeteris speciei suae varietatibus (necnon ab omnibus speciebus M. sensitivae arete affinibus) caulibus tetragonis, angulis antrorsus setulosis parce retro-aculeatis et intervallis planis glabris, petiolisque trigonis dorso carinatis ventre depressis bisulcatis diversa; foliolis lanceolato-ellipticis M. vellozianam revocans, sed legumine parvo setaculeato omnino cum M. debili congrua.—Brazil. Mato Grosso: ±30 km s. of Xavantina, 400 m, 11.VI. 1966 (fl, fr mat), Irwin (with Grear, Souza & Reis dos Santos) 16996. —Holotypus, UB; isotypi, G, K, LE, NY, R, US.

    Leaning or scandent subshrubs 1-2 m, the 4-angular stems forwardly and remotely retro-aculeate on angles but glabrous on plane faces, the lfts glabrous or remotely ciliate along midrib; leaf-stalks 2.5-6.5 cm, trigonous, keeled dorsally, flattened and shallowly bisulcate ventrally; lfts of distal pair obliquely lance-elliptic or elliptic-acuminate 3-6 x (0.6-)0.7-2 cm, 3-5 times as long as wide, the anterior proximal lft of each pinna cordate; capitula prior to anthesis moriform, the bracts ±0.6 mm; fl-buds minutely puberulent; pods 10-17 x 3-4 mm, the replum charged along dorsal and lateral ribs with straight, stramineous purplish-tipped setae to 1.5-3.5(-4) mm, the green or anthocyanic valves thinly setose over each seed, otherwise glabrous.

    In cerrado, in seasonally wet campo, and at gallery-margin, near 400 m, known only from the sources of rio das Mortes between Xavantina and Barra do Garças, lat. 14°30'-16°S in s.-e. Mato Grosso, Brazil.—Fl. IV-VI. Map 53.

    I have long hesitated over the taxonomic rank appropriate to this strange mimosa, which is unlike any other member of its subseries in having square stems and triquetrous, ventrally bisulcate leaf-stalks. In color and shape of leaflets the foliage of var. amnis-mortium suggests M. velloziana, but the plant is less densely prickly and the small hispid pod is precisely that of M. debilis. The venation of the leaflets is almost that seen in M. nuda var. glaberrima, but the marginal nerve is attenuated between setiform cilia and does not form a continuous homy rim.