Monographs Details: Chamaecrista nictitans subsp. disadena var. disadena
Authors:Howard S. Irwin, Rupert C. Barneby
Authority: Irwin, Howard S. & Barneby, Rupert C. 1982. The American Cassiinae. A synoptical revision of Leguminosae tribe Cassieae subtrib Cassiinae in the New World. Mem. New York Bot. Gard. 35, part 2: 455-918.
Family:Fabaceae
Synonyms:Cassia disadena Steud., Chamaecrista seleri Rose, Cassia seleri (Rose) Lundell, Chamaecrista chiriquensis Britton & Rose
Description:Species Description - Erect or rarely diffuse, essentially herbaceous and commonly monocarpic but in age basally suffruticose herbs at anthesis (3-)5-16(-20) dm, commonly both puberulent with short incurved hairs and the stems distally with leaf-stalks and sometimes the pedicels hirsute with spreading fine setae up to 1-2.4 mm, but either type of vesture sometimes sparse or 0, the subconcolorous lfts often dorsally, exceptionally also ventrally puberulent, rarely pilosulous, the margins either minutely ciliolate or randomly setulose, exceptionally glabrate. Stipules lance-acuminate or attenuate, those at flowering nodes (7—)8— 14(— 17) mm, at base (1.3—) 1.5—2.6(—2.8) mm wide, from base (7-)9-15-nerved. Adult lvs (3—)3.5—10.5(—13.5) cm, shortly petioled, the expanded blades lanceolate or narrowly ovate in outline; petiole (including pulvinus) 3-5.5(-8) mm, at middle 0.4-0.75(-0.8) mm diam, narrowly margined; petiolar glands 1—2(—3), the first (or only) one situated at, below, or above middle of petiole proper, in profile trumpet-, urn-, or broadly club-shaped, sometimes coarsely urceolate-turbinate (0.5—)0.6—1.6 x (0.25—)0.35—0.8(—1.2) mm, at least a trifle (often much) taller than the diam of the circular head; sometimes smaller glands on rachis below 1-5 distal pairs of lfts; lfts of adult lvs (10—) 12—24(—26) pairs, linear to narrowly oblong or linear-elliptic, mostly obtuse and abruptly apiculate or aristate, the larger up to (7-)9-22(-25) x 1.4-3.4(—3.7) mm, at base on broad side cordate or obtusely angulate, on narrow side broadly cuneate to subcordate, the costa varying from centric to moderately displaced, dividing the blade 1:1-2, from base on broad side shortly 3-4- and on narrow side 1-2-nerved, the costa pen- ninerved with (3-)4-6(-7) major secondary venules with sometimes additional intercalated ones, then appearing 8-12-nerved on either side, the venulation commonly impressed on upper and finely prominulous on lower face, exceptionally subimmersed on both. Peduncles adnate through (l-)2-14(-26) mm, (l-)2-5-fld; pedicels at anthesis weak subfiliform 4-11 mm, in fruit spreading-ascending thickened straight or incurved distally, (4-)6-14(-21) mm; buds ovoid-acuminate, thinly pilosulous or incurved-puberulent, sometimes glabrate distally; sepals lance-acuminate (6—)6.5—12 mm, petals yellow, 3 adaxial oblanceolate to narrowly obovate-cuneate, 6-10 5(-l l) mm, 1 long petal obovate-flabellate (7-)8-14(-15) x 5.5-10.5 ( -12) mm, the cucullus obliquely reniform 5-10(-12) mm; stamens 10, the anthers yellow, or red (drying blackish), the 2-3 long ones (5-)5.5- 10.5(-12.5) mm; ovary either strigulose or pilosulous; style linear, gently incurve or straight, 3-5.5 x 0.2-0.4 mm, not or only very obscurely dilated distally; ovules (11-)13—26. Pod linear, slightly arcuate, (30—)35—63(-70) x (2.5-)3-4(-4.4) mm, the green, brown or deep reddish- or purplish-castaneous valves shortly incurved-pilosulous or -puberulent, less often thinly setose; seeds fulvous or fuscous, dull, 2.6-3.7 mm, the testa lineolate-pitted.—Collections: 122.

Distribution and Ecology - Savannas at low and middle elevations, in Central America ascending into the pine-oak belt up to 2100 m, in Guayana and within the Amazonian Hylaea occupying scattered sunny habitats along rocky stream banks, islands in river-rapids, rock-outcrops, beaches, and becoming weedy in capoeira or cultivated ground, in coastal Bahia a common and locally abundant weed of roadsides and cocoa plantations but ascending inland to cerrado habitats up to 1200 m, of discontinuous range: Central America from Oaxaca (Cerro Zempoaltepetl, near 17°N, 86°W) s.-e. to w. Panama (Chiriquí); llanos e. of Cordillera Oriental in n.- e. Colombia (Norte de Santander; Int. Meta); Cordillera Costanera (Distrito Federal, perhaps a waif) and middle Orinoco valley (Cerro San Borja, Bolívar) in Venezuela; interior Guyana, Surinam, and adjacent Amapá and Terr. do Roraima in Brazil, from the upper Mazaruni, Rupununi and Courantyne valleys to the Wilhelmina and Tumucumaque ranges on the Jarí-Oiapoque watershed; somewhat disjunct along middle Amazon valley in Amazonas between Manacapurú and Purequequare (59°40'-60°40'W) with one record from upper Rio Negro (Vaupés) near 67°W; again disjunct along the Atlantic lowlands of n.-e. Brazil in Ceará and Bahia, extending occasionally inland to Chapada Diamantina (Sa. do Sincorá) and thence s. into n. Sa. do Espinhaço near 17°S in n.-centr. Minas Gerais; one record from n.-e. Paraguay (Río Apa, near 22°S).—Fl. in Central America mostly VIII-I, in the Guianas, Amazonia and e. Brazil almost throughout the year.

Discussion:

Like other discontinuously dispersed varieties of Ch. nictitans, the var. disadena consists of numerous races minutely distinguishable by proportions and coarseness of the petiolar glands, relative proportions and position of the duplex vesture, and length of the pedicels and flower parts. The nomenclaturally typical form, from Surinam, closely matched by modern collections from the Wilhelmina Mts. and Sa. Tumucumaque and from the headwaters of Rio Branco in Terr. do Roraima, has usually two slenderly stalked petiolar glands, setose stems, and long narrow puberulent pod containing some 14—26 seeds; but the flower varies in size from one collection to the next, the feature common to all being the linear style, on which we ultimately depend for separating var. disadena from the very closely related var. pilosa. The populations found in coastal Bahia, largely derived from roadsides and cocais, are essentially typical, but have usually only one petiolar gland. In riparian and disturbed habitats along the middle Amazon valley in Amazonas var. disadena is represented by a robust form with thinly puberulent or glabrate, when dry brownish foliage and stems, coarsely urceolate glands and a thinly setose, not puberulent pod of which the sutures are sometimes dilated into incipient wings. This form, collected first by Spruce near Manaus and in sliehtly more pubescent form by the Schomburgks in Guyana, was misinterpreted by Bentham (1871, p. 577) as C. riparia H.B.K. (of which the typus represents the short-styled var. jaliscensis) and treated by him as specifically distinct from "C. stenocarpa. " At anthesis it closely mimics subsp. patellaria var. praetexta, which replaces it on savannas of the lower Amazon valley; this differs in the smaller flower with short-styled ovary setose on the sutural angles but not on the faces, and when adult, of course, in the remarkable wing-margined pod. While it is readily recognized in Amazonas, on the savannas of interior Guyana it fades imperceptibly into typical var. disadena found in similar habitats immediately to the east and west. The one collection of this glabrescent form from the upper Rio Negro is peculiar for the presence of glands on several distal segments of the leaf-rachis, a phenomenon now known to occur in many distantly related forms of supra-axillary chamaecrista.

The var. disadena of southern Mexico and Central America, found largely (but not exclusively, e.g. typus of Ch. chiriquensis) in relatively undisturbed upland habitats associated with pine- or oak-forest, has the vesture and (1 or 2) glands of typical disadena, but a fewer (mostly 11-15- not 14-26)-ovulate and in consequence shorter pod, suggesting that of the entirely West Indian Ch. glandulosa var. swartzii, different in its fruticose adult stature and short stipules. The also closely similar Ch. glandulosa var. flavicoma, allopatric in the Andes (and in disjunct stations in Yucatan and southern Mexico) is only arbitrarily separable by the once again potentially shrubby or arborescent life-form and the usually very long, at anthesis flexuous pedicels.

One collection of var. disadena from Ceará (20 mi inland from Fortaleza, G. Bolland s.n., K) deserves special mention. With the habit of the coarse glabrate Amazonian race mentioned above but setose stems and leaf-stalks it has exceptionally large flowers (calyx and long abaxial petal to 15 mm and long anthers 12.5 mm) and the calyx lobes are prominently several-striate, not indeed so closely parallel-venulose as those of Ch. calycioides, but more prominently than those of any other New World chamaecrista known to us. Since Ch. calycioides was collected with it (Bolland s.n., K) it may not be fanciful to suppose an exchange of genes between the two, however unlikely that may appear from the assumed difference in chromosome number.

In adopting for this varietal taxon the epithet disadena, we deliberately pass over the earlier and probably relevant stenocarpa for two reasons: we have failed to typify C. stenocarpa Vogel with assurance; while its shifting application by Bentham, Britton and others to related members of the Ch. nictitans complex, particularly to what we here call var. pilosa, var. jaliscensis, and var. disadena in part only, have eroded its utility in practical taxonomy. The protologue of Cassia stenocarpa is based on two plants lost in the Berlin disaster, one collected by Sellow, of which we have not knowingly seen any duplicate, and one by Luschnath from Bahia, unfortunately not further identified as to number, date or place. Bentham equated C. stenocarpa with the Luschnath collection, supposedly from Ilhéus, that was distributed as Martius Herb. No. 720. A duplicate of Martius 720 at Berlin survives as Field Negative 1749, but if this is the Luschnath specimen seen by Vogel there is nothing on the label to prove it. Bentham (1870, p. 174) cited as C. stenocarpa a specimen collected at Cruz de Cosme by Martius; the duplicate in Bentham’s herbarium has short but linear styles. So far these all appear to represent our var. disadena. We have seen also, however, in the Vienna herbarium a Luschnath 193 and at Kew Luschnath 834 from the same locality, the former dated August 1835, both of which represent the short-styled relative var. pilosa. There is nothing decisive in the protologue pointing to one or other of the two entities known to occur in the Luschnath collection. By contrast the type-set of C. disadena is widely dispersed, unambiguous, and of excellent quality.

Distribution:Bahia Brazil South America| Oaxaca Mexico North America| Panama Central America| Chiriquí Panamá Central America| Colombia South America| Norte de Santander Colombia South America| Meta Colombia South America| Distrito Federal Brazil South America| Bolívar Colombia South America| Venezuela South America| Guyana South America| Amapá Brazil South America| Roraima Brazil South America| Mazaruni Guyana South America| Rupununi Guyana South America| Amazonas Guyana South America| Vaupés Colombia South America| Ceará Brazil South America| Minas Gerais Brazil South America| Paraguay South America|