Chamaecrista repens

Title

Chamaecrista repens

Authors

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Chamaecrista repens (Vogel) H.S.Irwin & Barneby

Description

35. Chamaecrista repens (Vogel) Irwin & Barneby, comb. nov. Cassia repens Vogel, Syn. Gen. Cass. 60 & Linnaea 11: 712, descr. ampliat. 1837.— Typus infra sub var. repenti indicatur.

Perennial herbs with 2-several simple or few-branched, amply leafy stems 1.5-11 (-14) dm arising from the crown of a woody taproot or from divisions of a sometimes subterraneously branched caudex, fully herbaceous or sometimes suffrutescent in age, variably puberulent or pilosulous with short incurved or short spreading, filiform or bulbous-based hairs and sometimes in addition longer spreading setae, the longer trichomes up to 0.4-1.4 mm, the foliage bright green, olivaceous or gray-olivaceous concolorous, the lfts varying from glabrous on both or only the upper face and ciliolate or rarely setose-ciliate to densely gray-pilosulous throughout, the lvs of mature plants commonly reduced at several shortened distal nodes and the inflorescence becoming pseudo-racemose.

Stipules erect persistent, narrowly lanceolate or narrowly ovate-acuminate, 2.5-8(-10.5) mm, at ± oblique base 0.7-1.6 mm wide, obscurely rounded to subcordate on broader side, from base prominently 5-8(-10)-nerved, the blades either glabrous or pilosulous dorsally, nearly always ciliolate.

Lvs at middle of flowering stems up to 2.5—10(—11) cm, those at the lower and uppermost nodes shorter, all shortly stout-petiolate, the expanded blade ovate to lanceolate or lance-elliptic in outline, the distal and often the first pairs of lfts smaller; petiole including pulvinus 3—8.5(—10) mm, at middle rather broadly margined and (0.45—)0.5—1.2(—1.5) mm diam, the marginal flanges commonly forced apart by the massive gland so as to form, in dorsal view, a pronounced nodule; gland almost always solitary, situated near middle or at top of petiole proper, in outline round, deeply concave, coarsely smooth-margined, (0.4-)0.5-l mm diam, elevated on a broad mounded, commonly pilosulous pediment (dilated stipe), the whole in profile 0.5-0.9 mm tall, at base 0.65-1.5(-l.6) mm diam, at least a trifle broader than high, but the stipe becoming in some populations of var. multijuga cylindric and the whole gland drum-shaped in profile; lfts of adult median lvs (4-) 5-19 (-20) pairs, relatively well-separated along rachis, in outline varying from linear-oblong to oblong-elliptic or -obovate, straight or falcate, obtuse to subemarginate or exceptionally subacute, abruptly mucronulate or spinulose, the largest (10-)12—23 (-27) x (2-)2.5—8 mm, at strongly asymmetric base cordate or cordately angulate on the broad side, from base prominently 6-9(-l l)-nerved by the subcentric to strongly excentric midrib with on the broad side 4-6(-7) and on the narrow one (0-)l-2(-3) veins, the costa thence penniveined, with 4—7(—8) pairs of major secondary and often as many almost as strong intercalated venules, the venation prominulous on both faces but often more sharply so beneath.

Peduncles with raceme-axis (2—)3—13(—15) mm, the peduncle adnate throughout or free up to 3 mm, the axis 0—3.5 mm, 1—4(—5)-fld; pedicels ascending, at anthesis slender 4—14 mm, in fruit thickened and 6—23 mm (or at some distal nodes shorter), bracteolate 1-5 mm below calyx; bracteoles ovate or lanceolate 1.3-3 mm; buds narrowly ovate-acuminate, thinly pilosulous and rarely also randomly setose; sepals commonly brownish or reddish-tinged, lance-acuminate or the inner ovate- acute, 8.5—13.5 mm; petals yellow fading orange, 3 adaxial oblanceolate to narrowly elliptic-obovate, (7.5—)8—15 x (2.5-)3.5-8 mm, 1 abaxial flabellate to broadly obovate, (10—) 11—19 x 7-12 mm, the cucullus semi-obovate, obliquely reniform or falciform 11—20.5 mm; stamens 10, the long anthers 7—12 mm; ovary densely gray strigulose; style linear, gently incurved, (2.5-)3.5-7 x 0.2-0.4 mm; ovules (7-) 10-22.

Pod erect or stiffly ascending, linear, slightly arcuate, (25-)35-70 x (3-)3.5-4.7 mm, the reddish-brown or purplish-castaneous, ultimately nigrescent valves minutely puberulent, shortly thinly pilosulous, or rarely remotely setulose; seeds (little known) 2.6-3.3 mm, the dull fulvous or sooty testa blackish-punctate.— Fig. 2 (petiolar nectary).

As here redefined in more comprehensive terms, the inappropriately named Ch. repens differs from related South American chamaecristas with large, supra- axillary flowers chiefly in its curious and characteristic (even though in fine detail variable; see note under var. multijuga) petiolar gland, which is so stoutly stipitate as to appear perched on a mounded or rarely columnar, usually puberulent pediment at least as wide and ordinarily wider than itself. Variation in number and venation of the leaflets supports the recognition of two geographically disjunct varieties, a southern, largely extra-tropical and extra-Brazilian var. repens with relatively few, subsymmetric leaflets, the range of which is centered on the lower Paraguay-Paraná basin; and an endemic Brazilian var. multijuga, widespread around the São Francisco basin from western Minas Gerais northeastward to inland Maranhão and Ceará, different in the more numerous, variably but always decidedly oblique leaflets, often but not consistently coinciding with a more erect and more robust habit of growth. Apart from the gland, the detached leaf of var. repens closely resembles that of Ch. nictitans var. brachypoda, vicariant northward on the Brazilian Planalto, but this is readily distinguished in the field by its monopodial monocarpic wandlike life-form and, when closely observed, by the larger, multistriate stipules and sessile patelliform or turbinate gland. Granted the same reservations about the petiolar gland, the leaf of var. multijuga is almost that of the distantly allopatric Argentine Ch. venturiana which resembles the dwarf and diffuse var. repens in habit, and is only somewhat arbitrarily excluded from Ch. repens sens, lat., a point discussed in the foreword to ser. Chamaecristae.

Variation in composition and density of vesture, everywhere rife in sect. Chamaecrista, is especially marked in Ch. repens, where it occurs both within and between populations and equally in each variety, the leaflets changing imperceptibly from bright green, glabrous and sharply striate-veined on both faces to gray- pilosulous and only obscurely (cryptically) venulose, or both pilose and striate. A feature of the species as a whole, seen however only in mature flowering and fruiting individuals, is the often sudden reduction in size of the upper leaves, exposing successive fascicles of flowers or pods in a sort of interrupted virgate raceme. The pinnate venulation arising from the midrib of the leaflets varies in number and emphasis of venules intercalary to the always raised 4-7 pairs of major secondaries; and in var. multijuga in the development of one pronounced primary vein arising next to the midrib on the leaflet’s broad side and produced nearly or quite to the blade’s apex. This last pattern characterizes the relatively narrow and falcate leaflets of the typus of C. drepanophylla, but occurs sometimes on the same plant with broader leaflets normally veined.

The small sample seen by Bentham (1870, 1871) provided only a defective and distorted view of the real Cassia repens and C. drepanophylla, taxa which emerge in modern experience as so closely related as to be no longer separable at the specific level. Bentham referred the two species to different series in sect. Chamaecrista, C. drepanophylla to ser. Coriaceae, from which it is handily excluded by the supra-axillary inflorescences, and C. repens, because of its relatively few leaflets, to ser. Subcoriaceae. An obscure C. brachypoda var. multijuga, based on a collection simultaneously (and correctly) associated by Bentham with C. drepanophylla, provides our varietal epithet.