Cassia chartacea var. chartacea

Erect shrub or subshrub, usually much-branched, to 1.5 m. Stems puberulent or pubescent when young. Stipules partly obscuring upper stem, lanceolate-cordate or narrowly ovate-cordate, long-acute or -acuminate, 6.1-9.0 mm long, 2.0-3.1 mm broad, glabrous, often somewhat glaucous, ciliolate. Petiole slender, 4.2-6.0 mm long, the adaxial groove puberulent, the abaxial surface pubescent or pilose with distally-directed hairs; rachis 0.3-0.5 as long as petiole, often arched upward. Gland 1, usually scutellate, 0.2-0.4 mm broad, sessile, often depressed and obscure. Leaflets bijugate, rarely trijugate, the pairs subequal or the superior pair slightly longer, joined to rachis by a small arcuate black, brown or yellowish pulvinule 0.2-0.5 mm long, oblanceolate, slightly oblique, straight or the superior blades occasionally divergent, glabrous, often glaucous, membranaceous or papyriferous, 1.2-2.5 cm long, 0.3-0.5 cm broad, gray-green; margins frequently ciliolate at the rounded or obtuse apex. Flowers usually solitary; pedicels straight, somewhat flattened, unilaterally or wholly puberulent, 1.6-2.1 cm long and ca. 0.3 mm thick in flower, up to 2.8 cm long and 0.5 mm thick in fruit; bracts 2, lanceolate to ovate, 2.0-3.1 mm long, 0.7-1.4 mm broad; bracteoles subopposite, lanceolate, 3.9-5.1 mm long, 1.2- 1.4 mm broad; sepals lanceolate or narrowly ovate, glabrous, 1.0-1.4 cm long, 2.7-3.4 mm broad; petals 1.2-1.6 cm long, 0.9-1.4 cm broad, the banner occasionally with a pink blotch (e.g. Irwin 2420) ; ovary yellow- or gray-pilose. Pod narrowly oblong, 2.7-3.4 cm long, 4.5-5.7 mm broad, flat or nearly so, sparsely appressed- pilose. Seeds 10-15, slightly compressed, 4.0-4.2 mm long, 0.7-1.2 mm broad.

Chromosome number: not determined.

Distribution: Brazil, central and western Minas Gerais and southern Goiás south to central and western São Paulo. Possibly also in western Pernambuco and in central Paraná. Occurring in rocky and sandy hills and savannas, from 750 to 3000 feet elevation.

Cassia chartacca, named for the unusually thin and obscurely veined leaflets, is based on a number of collections, showing considerable homogeneity in the typical variety, which were first recognized by inference as a taxonomic entity by Bentham. However, in his treatment of Cassia in Flora Brasiliensis, Bentham, who cited Martius 1076 under C. uniflora,¹⁴ evidently adopted a different concept of that species than was intended by Sprengel. This is clear from Sprengel’s type description of C. uniflora Spreng., in which C. lanceolata Pers., while listed as a possible synonym, is later in the same description regarded as agreeing with C. uniflora in all details save those of the stipules. However, the type of C. lanceolata clearly agrees with C. tetraphylla Desv. var. brevipes (Benth.) Irwin. Colladon's (1816) type description of C. persoonii similarly treats C. lanceolata as a synonym.

In his monograph of the genus (1871) , Bentham placed C. lanceolata and C. persoonii in synonymy under C. uniflora, but without having seen the types for any of the 3 names. Thus, it is clear that Bentham’s concept of C. uniflora was not gained as a result of critical study of specimens but rather from the wholly inadequate diagnoses of the authors mentioned. It is clear that C. uniflora and C. persoonii are based on the Lamarckian specimen which typifies C. lanceolata; because the last, clearly part of the C. tetraphylla complex, has been treated as a synonym of C. uniflora and C. persoonii, the material at hand requires separate documentation as C. chartacea.

Careful study of material assignable to C. chartacea has shown that in 3 areas in Minas Gerais and southern Goiás characters of this species tend to approach those of C. langsdorffii Kunth var. parvifoliola Irwin. In specimens from the first of these areas, southern Serra do Espinhaço, from Serra do Cipó northward to the vicinity of Diamantina, leaflets are often smaller, more apiculate, firmly membranaceous or subcoriaceous, the pedicels up to 0.7 mm thick in fruit, and the petiolar gland frequently long and somewhat stipitate. Material from the mountains immediately east of Belo Horizonte, i.e. from Itabirito to Ouro Preto, differs from the more northerly variant in having leaflets more nearly the size of those in the typical C. chartacea, but with longer stipules, very like those of C. langsdorffii var. parvifoliola. The third "region" is much less well defined and, judging from the few specimens now available, may not be a discrete region but simply a collection of isolated localities where sympatric hybridization and consequent introgression has occurred. These variants, from western Minas Gerais (Patos de Minas, Serra do Caracól) and southern Goiás (Chapada dos Veadeiros), are similar in having even larger stipules, i.e. up to 1.4 cm long, unilaterally puberulent pedicels about as long as the stipules in fruit, and subsessile petiolar glands ca. 0.5 mm broad. Although both C. langsdorffii var. parvifoliola and the typical C. chartacea are sympatric in São Paulo, there are no known intergrades from that state. However, in lieu of actual field knowledge of the populations from which the above described specimens were obtained, it is felt that formal recognition should be deferred until the central Brazilian region becomes better known.

A fourth variant, found on the savannas of Bahia, Minas Gerais, São Paulo, and Paraná, is distinctive in its low, decumbent, ramose habit, its smaller but still membranaceous leaflets, and its narrower stipules. Because the taxonomy of the Xerocalyx species is relatively uncomplicated south of Minas Gerais and because of the apparent stability of this variant, it will be dealt with separately as C. chartacea var. tenuicaulis Irwin.

C. uniflora var. latifolia Benth., with larger foliar structures and corollas approaching those of C. tetraphylla in size, resembles typical material of C. chartacea in other respects, and is therefore included here.