Mimosa albolanata

Title

Mimosa albolanata

Author(s)

Rupert C. Barneby

Scientific Name

Mimosa albolanata Taub.

Description

239. Mimosa albolanata Taubert, Bot. Jahrb. Syst. 21: 433. 1896.—Typus infra sub var. albolanata indicatur.

Amply leafy unarmed subshrubs, the stems of the year including terminal, simple or weakly branched pseudoraceme (1—)2—10 dm, either erect and wandlike or stiffly ascending from a xylopodium or from a framework of prostrate, sometimes adventitiously rooting woody trunks exceptionally attaining 1 m in length, at anthesis either efoliate except for subradical lvs or leafy to middle, but lvs at most flowering nodes hysteranthous, developing pari passu with the pods and becoming longer than them, the cauline and foliar axes variably strigose- or silky-setose with tapering or slenderly flagelliform lustrous setae to 2-6 mm, nowhere glandular, the margin of the facially glabrous, rarely puberulent lfts varying from glabrous to scaberulous or from villosulous to weakly setose. Stipules firm, lanceolate or triangular-acuminate (5—)6—17(—19) x (1.5)-2—4.5(-6) mm, densely setose externally, glabrous castaneous within, either persistent or caducous. Leafstalks (9-) 13-28 cm, the petiole including obese pulvinus 0.5-3.5(-4) cm, the longer interpinnal segments 10-21 (-26) mm, the ventral groove either continuous or bridged between pinna-pairs but spicules 0; pinnae (9-) 10-30(-32)- jug., strongly decrescent proximally but less or scarcely so distally, the rachis of longer ones 3- 7(-9) cm, the longer interfoliolar segments (0.8-) 1-2.3 mm; lfts of longer pinnae (18-)22- 44(-55)-jug., the first pair close to pulvinus (paraphyllidia 0), all in outline narrowly oblong but sometimes a little dilated toward oblique base, the larger ones (2.8-)3.2-9 x (0.8-) 1-1.8 mm, all smooth and veinless above, often becoming obtusely 3-nerved beneath. Peduncles solitary or 2-3 together, 0-4.5(-7) cm; capitula broadly ovoid or globose, without filaments 10-16 mm diam., prior to anthesis conelike silky-setose; bracts oblanceolate, oblance-elliptic or spatulate 3-6(-8) x 0.5-1.2 mm, setose marginally and at least thinly so dorsally, usually shorter than or equalling the expanded fl, rarely surpassing it; flowers 4-merous 8-androus, some lower ones staminate but scarcely shorter; calyx-tube membranous, commonly 0.3-0.8, exceptionally 0.7-1.5 mm, glabrous externally, the truncate or irregularly lobulate rim ciliate with setulae (0.3-)0.5-2.5 mm; corolla (3.5-)4-6 mm, the ovate lobes densely or thinly setulose dorsally; filaments pink, monadelphous through 0.7-1.2 mm, the longer ones exserted (7.5-)8-14.5 mm. Pods (1—)2—8 per capitulum, sessile or almost so, in profile narrowly oblong or oblong-elliptic 25-50 x 9-15 mm, 5-11-seeded, the replum 1.5-3 mm wide produced into a terminal cusp (1 —) 1.5—7mm (this at times reduced to a scarcely differentiated triangular point), the valves composed of livid exocarp 0.3-0.5 mm and papery-crustaceous endocarp 0.1-0.2 mm thick in section, the replum and valves alike or the latter more densely charged with short tapering or flagelliform, appressed or forwardly ascending setae to (0.5-)0.7-2.5 mm, the turgidly low-convex valves separating entire from replum but long-persistent at base; seeds ovate or almost round in broad profile, 3.6-5 x 3-4 mm, the testa smooth lustrous dark-castaneous or livid-nigrescent.

I refer to the polymorphic M. albolanata those planaltine Pachycarpae that differ from compatriot kindred by proximally foliate homotinous stems not over one meter in length arising yearly from a xylopodium or from a humifuse, at times adventitiously rooting framework of woody branches. The mature plant is a subsessile or prostrate suffrutex that does not, like most forms of M. claussenii and M. foliolosa, acquire erect or ascending defoliate trunks, but dies back annually to the level of the ground. At anthesis the erect wandlike or stiffly assurgent, simple or few-branched fertile stem may be devoid of expanded leaves exept at a few subradical nodes or may bear mature foliage upward to mid-stem. However, the capitula at anthesis are commonly subtended by a hysteranthously expanding leaf that appears at that time only in primordial form but grows out rapidly thereafter and greatly surpasses the mature fruiting peduncle. In consequence there are marked differences between plants of one sort collected in flower and in fruit. Independently of seasonal dimorphism the mutually remote major populations of M. albolanata differ in size and propinquity of leaflets, in length of peduncles, in absolute and proportionate lengths of floral bracts and flowers (and hence in diameter of capitula), in depth of calycine cup and in length of its cilia, and in pubescence of the pods, these as yet incompletely known. None of the observed differences is truly constant even within the boundary of a particular locality, and I can discern in the group only an inchoate stage of differentiation. The key to geographic varieties that follows is imperfectly realized for it fails effectively to distinguish all of them at every stage of maturity.