Cassia fagonioides

  • Title

    Cassia fagonioides

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Cassia fagonioides Vogel

  • Description

    163.  Cassia fagonioides Vogel, Syn. Gen. Cass. 50. 1837.

    Humifuse or procumbently trailing, very viscid herbs with several or many diffusely branching, rarely almost simple stems (2-)3-20 dm radiating from the crown of a slender blackish taproot or at length knotty caudex, viscid-villosulous and hispidly setose almost throughout but the vesture variable in composition and density, the villosulous hairs sometimes few or fully suppressed, the setae usually up to 1-2(-2.4) mm but rarely reduced to setules scarcely longer or coarser than the villi, the thin-textured subconcolorous lfts usually villosulous both sides and ciliolate, sometimes also setulose on lower or exceptionally both faces, or the faces rarely glabrate, the margins only exceptionally glabrate, the loosely or remotely few-fld racemes terminal to branchlets, all sessile, the first fl subtended by a developed leaf.

    Stipules weakly spreading-ascending, commonly deflexed in age, subherbaceous, green or reddish, triangular-subulate to linear-lanceolate, (0.8-)1-3 mm, persistent.

    Lvs widely spreading-ascending or those of the upper stems often declined, mostly 1-4.5 sometimes up to 5-6 cm, slender-petioled; pulvinus not or scarcely differentiated, sometimes discolored, up to 1.2 mm; petiole usually very slender, 4-18(-23, exceptionally -28) mm, at middle 0.2-0.4 mm diam, very narrowly green-margined and sulcate ventrally, not over 1.5 times as long as the lower pair of lfts; rachis (2-)3-8(-11) mm; lfts 2 pairs, of uniform size or the distal a little longer, by day spreading or the distal one tilted forward, face upward, on scarcely dilated pulvinule 0.5-1.1 (-1.4) mm, at night tilted groundward and folded face to face, in outline obovate, obovate-elliptic, or more rarely oblong-elliptic or suborbicular, obtuse or emarginate, muticous or minutely mucronulate, 4-26 x 2.5-19 mm, at asymmetric base rounded to subcordate on proximal side, cuneate to rounded on the opposite, the margins entire, plane or narrowly revolute, the blades submembranous or chartaceous, on both faces olivaceous and dull or glutinously sublustrous, or beneath sometimes a little paler and glaucescent, almost always ciliolate and commonly also villosulous or both villosulous and setulose both sides, rarely glabrescent or glabrate, the slender midrib prominulous beneath and often above also, at least beneath connected by some few sharply prominulous tertiary venules.

    Racemes 3-45-fld, all terminal, the relatively stout and many-fld early ones surpassed by secondary and succeeding sympodial axes, sessile on a branchlet of one internode, the first (rarely 2-3) fl subtended by a lf, the later few-fld racemes sessile and terminal to very slender or subcapillary branchlets and often exserted, the axis commonly becoming flexu- ous, in fruit 1.5-30(-40) cm, the one expanded fl displayed below the level of the loosely but shortly racemose buds; bracts spreading, herbaceous, ovate or lanceolate, 1.5-3.5(-4) mm, persistent; pedicels at anthesis ascending, in fruit straight and divaricate, or sigmoid, or deflexed and geniculate under the pod, 1.3-4 cm, bracteolate 1 — 12 mm below calyx, the lowest on a raceme often longer than later ones; bracteoles like bracts, but mostly subulate, 0.7-1.8 mm, persistent; buds plumply ovoid to globose, very obtuse, villosulous and setose; sepals submembranous, brownish or greenish, oblanceolate to elliptic-obovate obtuse, 4.5-10.5 x 1.6-5.4 mm; petals vivid orange varying through salmon-pink to ruby red, fading pinkish or brownish-orange, sometimes yellow when dry, 4 alike or nearly so, ascending at ±40°, spatulate or broadly oblanceolate-cuneate, abruptly or attenuately narrowed into the claw, rounded or truncate at apex, the longest of them 7-17 mm, the fifth falcately half ovate, nearly as long or slightly longer but incurved over the androecium; ovary setose; ovules (4-)5-7.

    Pod linear-oblong, often a little curved downward, (20-)25-37 x 4.5-7.5 mm, the valves viscously villosulous and usually densely hispid, the setae pale, up to 2-5 mm; seeds 2.7-4.7 mm, the testa black or atrocastaneous, highly lustrous, lineolate.

    A weedy, essentially herbaceous, usually very sticky cassia with profusely branching, pliantly prostrate stem, C. fagonioides is notable for its usually vivid orange flowers produced in small number over a long season. It has been often confused with or subordinated to the related C. tetraphylla, but is distinguished with ease by its softer, mostly deflexed stipules, its relatively short petioles, its thin-textured venulose leaflets usually pubescent both sides, its obtuse sepals and hence rounded flower-buds, and its orange-tinted, not golden yellow petals. An almost constant differential character is the presence of a leaf subtending the first (sometimes the second or even the third) flower of every raceme, a feature never encountered in C. tetraphylla, in which the lower, leaf-opposed racemes are shortly pedunculate and naked, not elevated on a branchlet of one internode. The foliage of C. tetraphylla varies from glabrous to villosulous and setulose, but the more pubescent forms of it occur very rarely outside of Central America and thus only exceptionally within the range of C. fagonioides var. fagonioides, which differs further in its much shorter calyx (sepals ± 5-7, not 8-13 mm) and smaller (± 2.5-3.5 not 4-6.5 mm) anthers. The allopatric C. fagonioides var. macrocalyx alone rivals C. tetraphylla in flower-size, but its prominently venulose leaflets combined with blunt flower-buds and orange petals are entirely distinctive.

    The racial situation within C. fagonioides is complex, reflecting a far-flung, apparently discontinuous dispersal, but analysis of the material before us has brought to light only one substantial discontinuity, between a usually coarse-stemmed, large-leaved, large-flowered var. macrocalyx, widespread over the highlands of interior southeastern Brazil, and a small-flowered var. fagonioides which occurs on the Planalto only locally in southern Minas Gerais, extending thence north around the continental coastal plains and nearby Atlantic slope to British Honduras. The considerable diversity in leaf-size and pubescence within each variety is mentioned further below.

    Key to the varieties of C. fagonioides

    1. Sepals 4.5-6.5 x 1.7-3.2 mm; longest petals 7-13 x 3.2-7 mm; anthers 2-3.5 mm; seeds 2.7-3.5 mm x 1.8-2.2 mm; planalto of Brazil only in s. Minas Gerais, thence n. around the coastal plain and Atlantic and Caribbean slopes from Esplrito Santo to Panama; disjunctly in British Honduras, adjoining Peten, and s. Mexico.

    163a. var. fagonioides

    1. Sepals (7.5-)8-10.5 x 3.4-5.4 mm; longest petals (12-) 13-17 x (5.5-)7-12 mm; anthers 3.1-4.2 mm; seeds 4.2-4.7 x 2.6-3.5 mm; Planalto of e. Brazil, from s. Maranhao (upper Rio Parnaiba drainage) and s. Piaui to s. Mato Grosso and the Triangulo Mineiro.

    163b. var. macrocalyx