Mimosa townsendii

  • Title

    Mimosa townsendii

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Mimosa townsendii Barneby

  • Description

    16. Mimosa townsendii Barneby, sp. nov., foliorum petiolo plerumque nectario cupulari depresso instructo flosculisque tetrameris M. nothacaciae affinis, sed ab ea caulibus tantum at nodos aculeis geminis (nec secus angulos seriatim) aculeatis, petiolis inermibus, stipulis minimis (±1, nec 5—8 mm longis), necnon foliolorum costa valde excentrica diversa. — Ecuador. Loja: Cariamanga, ±2150 m, 24.XI.1910 (fl), C. H. T. Townsend 949.— Holotypus, US 534438 = NY Neg. 12186.

    Treelets armed at nodes of young branches with a pair of subhorizontal broad-based aculei 3—5 mm, puberulent throughout with plain hairs 0.1—0.2 mm, the stems densely loosely so, the sub-concolorous lfts finely strigulose on both faces, the young inflorescence a leafless (but hysteran- thously foliate) panicle of short fl-spikes. Stipules subulate 1 mm or less, early caducous. Leafstalks 4.5-11 cm, the petiole 8-13 x 1.1-1.6 mm, the interpinnal segments 5-7 mm, the ventral groove continuous and spicules 0 but a depressed circular nectary at tip of lf-stk and in many lvs also shortly below first pair of pinnae; pinnae 8-15-jug., the longer ones 3.5-4 cm, the interfoliolar segments 0.8-1.2 mm; lfts of longer pinnae 26-30-jug., a little decrescent at each end of rachis, the first pair ±0.5 mm distant from subulate paraphyllidia ±0.5 mm, the blades narrowly oblong from obtusangulate base, deltate at apex, those near mid-rachis ±3.5-4 x 1-1.3 mm, 3.5-4 times as long as wide, all nerveless above, beneath weakly 2-nerved from pulvinule, the midrib forwardly displaced to divide blade ± 1:4, the posterior nerve short and weak. Peduncles 1-3 per node, or 1 paired with a branchlet, at anthesis 1-1.5 cm; spikes dense, without filaments 8-15 x 4 mm, the minute caducous bracts much shorter than the obtuse, minutely puberulent fl-buds; flowers 4-merous 8-androus; calyx shallowly campanulate 0.5 mm, the minute depressed-deltate teeth at most 0.1 mm; corolla 2.3 mm, the ovate ascending 1 -nerved lobes 1.1 x 0.75 mm; filaments white, united at very base into a stemonozone ±0.2 mm, exserted 5 mm; ovary puberulent; pod unknown.

    In unknown habitat, but to be expected in xeromorphic scrub thickets near 2150 m, known only from the type-locality on the w. slope of the Ecuadorian Andes close to the Peruvian border, long. 79°40'W.-F1. XI-XII(-?).

    In petiolar nectaries both at tip of leaf-stalk and also in some leaves on leaf-stalk below the first pair of leaflets, as well as in the tetramerous flower, M. townsendii seems closely related only to M. nothacacia. From this it is strongly differentiated by armature of geminate, immediately infranodal, straight (not serially scattered uncinate) aculei, by tiny stipules and by displaced midrib of leaflets. In general habit and in paired cauline aculei it resembles some Andinae, but these are all innocent of extrafloral nectaries and have pentandrous flowers. Superficially M. weberbaueri appears most similar in leaf-formula and ellipsoid flower-spikes, but this is otherwise typical of Andinae.