Cassia ochnacea

  • Title

    Cassia ochnacea

  • Author(s)

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Cassia ochnacea Vogel

  • Description

    108.  Cassia ochnacea Vogel, Syn. Gen. Cass. 51 & in Linnaea 11: 696, descr. ampliat. 1837. —Typus infra sub var. ochnacea indicatur.

    Shrubs and undershrubs variable in habit, either dwarf and humifuse from a xylopodium or short caudex or erect and developing woody trunks with fissured bark, glabrous throughout or the stems, axes of inflorescence, sepals and pod variably villosulous but not or only very obscurely and minutely setulose, the coriaceous or firmy chartaceous lfts commonly concolorous, little or not differentiated dorso-ventrally, sometimes purplish-mottled beneath, equally veiny both sides, the faces usually glabrous except sometimes for a few hairs dorsally about the pulvinule (these exceptionally extending over the whole dorsal face), the simply racemose or incipiently paniculate inflorescence terminal and exserted.

    Stipules erect, firm, narrowly subulate, (1 -) 1.5-5 mm, persistent.

    Lvs mostly ascending at narrow angles, sometimes spreading or from humifuse stems becoming unilateral, 3-9.5 cm, petioled, the lowest shorter and simpler than the rest; pulvinus moderately dilated, ovoid, 1.5-2.5 mm, coarsely wrinkled when dry; petiole (4-)5-21 mm, 0.6-1.2 mm diam, narrowly suicate ventrally; rachis (0-)5-30 mm; lfts of some early lvs 1, of the rest 2-3(-4) pairs, tilted forward and turned obliquely edgewise to the meridian on stout firm, coarsely wrinkled pulvinule ± 0.8-1.4 mm, the distal pair commonly slightly larger, in outline oblanceolate, elliptic-oblanceolate, or narrowly to broadly rarely subrhombically obovate, (1 -) 1.5-6 x (0.6-)0.8-3.4 cm, obtuse or deltately acute but sharply mucronulate by the excurrent midrib, at oblique base cordate on proximal and rounded to broadly cuneate on distal side, the margin plane, entire, often red- or yellow-tinged, the blades coriaceous to stiffly chartaceous, mostly olivaceous on both sides and either dull or incipiently lustrous, sometimes glaucescent or dorsally olivaceous mottled with pinkish-purple, the centric straight tapering midrib and 5-15 pairs of usually widely divergent secondary nerves subequally prominent both sides, the tertiary connecting venules also raised on both sides forming an irregular reticulm of plane areoles up to ±0.5-1.5 mm diam.

    Inflorescence terminal to primary stems and sometimes to 1-2 leafless or thinly leafy subterminal branchlets, the axis of the densely many-fld racemes becoming 6-I5 cm, the several simultaneously expanded fls standing well below the racemose buds; bracts submembranous, narrowly lance-acuminate, (2-)3-9.5 mm, caducous from the buds long before anthesis but forming an imbricated coma around the tip of the immature raceme; pedicels ascending 3-12(-14) mm, bracteolate 1-2.5 mm below calyx; bracteoles resembling bracts (2-)3-5 mm, early deciduous; buds plumply ovoid, bluntly apiculate by the hooded exterior sepal, either glabrous or villosulous; sepals submembranous, red or yellow with pallid margins, oblong to lance-elliptic, obtuse, 8-11.5 x 2.6-4.4 mm; petals yellow or red-orange, when orange sometimes drying purplish, campanulately ascending at full anthesis, 4 subhomomorphous but of different lengths, the adaxial longer, broadly obovate-cuneate, to 12-17,x 6-9 mm, the fifth shorter, falcately oblanceolate, coiled; ovary glabrous, villosulous, or setulose; ovules 5-8.

    Pod oblong, sometimes curved downward, 3-5 x 0.7-0.9 cm, the brown or reddish valves finely cross-nerved; seeds unknown.

    A species of limited dispersal, except for the disjunct var. speluncae endemic to a segment of southern Serra do Espinha^o between approximately 18° 30' and 20° 30' S. latitude, C. ochnacea is nevertheless polymorphic, composed of populations differing in stature, in number, shape, and venation of the leaflets, in pubescence, and in color of the flowers. Features common to all are the few (1-4, mostly either 2 or 3) pairs of coriaceous or stiffly chartaceous, veiny leaflets little differentiated dorsoventrally and a terminal racemose inflorescence of many flowers spreading or somewhat nodding on short pedicels from which the bracts, which form a coma around the young buds, fall away long before anthesis.

    The typical form of C. ochnacea, described from a fruiting plant of which we have seen only a photograph accompanied by 2 leaflets and fragments of a pod, has 2-3 pairs of coriaceous, narrowly obovate-elliptic leaflets dorsally pubescent about the pulvinule, each with about 9-10 pairs of strong secondary nerves anastomosing into a prominently elevated submarginal vein, together with villosulous inflorescences and fruits. The stature and petal-color are unknown, and we have seen few other seemingly identical specimens, these collected in southern Sa. do Espinhaço (Serra d' Ouro Branco; Nova Lima).

    Closely resembling var. ochnacea in foilage, except that the commonly 2-jugate leaflets are quite glabrous, is the var. purpurascens, a procumbent undershrub with vivid orange or red-orange flowers that sometimes assume a purplish tint in drying. This variety, known only from Serra do Cipo and vicinity, is further characterized by its glabrous ovary and pod; its raceme and sepals are commonly glabrous like the rest of the plant, but Riedel obtained one branch with puberulent axis of inflorescence and thinly villosulous sepals, demonstrating the unreliability of pubescence characters in this species. The Serra do Cipo, a veritable cornucopia of Absus cassias, has yielded several interesting variants in one or another way intermediate between var. purpurascens and var. latifolia: a) combining the glabrous foliage, inflorescence and ovary and the procumbent stems of var. purpurascens with the obovate, relatively small and few-veined, commonly mottled leaflets and yellow petals of var. latifolia (Mello Barreto 8846; Irwin 2441; Hatschbach & Ahumada 31560); b) the same, but with pilosulous ovary (Sampaio 6587); and c) plants essentially like var. latifolia on Sa. de Cara^a except that the leaflets are quite glabrous dorsally and the stems are procumbent (Irwin & at. 20626). Since typical var. latifolia occurs also on the crest of Sa. do Cipo, but apparently rarely (Duarte 2632), in the form of an erect shrub to 2 m tall, there appears to be in this region a full series of intergradient stages between the idealized concepts of the varieties, possibly due to hybridization where they occur in close proximity. Pending the required field-study we refer provisionally to var. latifolia all those forms characterized by obovate leaflets lacking a strong intramarginal nerve, whether these are dorsally pubescent or not, or accompanied by glabrous or pubescent ovaries.

    The remaining forms of C. ochnacea are, so far as surely known, more erect shrubs or undershrubs developing strong woody trunks. Those found in Sa. do Espinhaço differ collectively from var. ochnacea and var. purpurascens in the rather thinner-textured, always obovate and always dorsally puberulent leaflets with about 5-8 pairs of secondary nerves anastomosing into a slender, undulate intramarginal one. The leaflets vary in number from two to four pairs; the inflorescence axis is pubescent; the petals so far as recorded are consistently yellow; and the pod (ovary) is glandular-setulose. The majority have stems smooth and glabrous up to the base of the terminal raceme, in this respect resembling the type of var. latifolia Benth., but two from the neighborhood of Belo Horizonte are distinguished from the rest by their densely shaggy-villosulous stems and seem reasonably set apart as a var. mollis. Remotely disjunct in southwest Minas Gerais is the apparently very local var. speluncae in which the broad leaflets of var. latifolia are curiously combined with the villosulous branchlets of var. mollis and the pronounced intramarginal nerve of var. purpurascens.

    The known dispersal of the varieties of C. ochnacea is probably quite incomplete, but already raises some difficulties. The known populations of var. ochnacea are separated, if the data are correct, by the length of the species-range,the type from Serra do S. Antonio, a place believed to be near Serro, and others from south of Belo Horizonte. The type-locality of var. latifolia is likewise a Serra do S. Antonio, but very likely not the same as that of Sellow. The holotypus of this variety is distinguished by a curious purple mottling of the leaflets' underside, matched only by one single modern collection from Sa. de Caraça. All well-documented stations for var. latifolia and var. mollis are situated on the east slope of a southern extension of Serra do Espinhaço, lying a short distance east and southeastward from Belo Horizonte.

    Disregarding the intermediate forms mentioned above, the varieties may be distinguished as follows:

    1. Ovary and pod glabrous; if of Sa. do Espinhafo, the foliage, axes of inflorescence and buds (sepals) all glabrous and the petals orange. Lfts stiffly coriaceous, the major secondary veins anastomosing distally into a stout intramarginal nerve almost as prominent as the midrib.

    2. Lfts broadly rhombic-obovate, like the branchlets and sepals at least thinly villosulous dorsally; major secondary veins of lfts ± 7-9 pairs; erect shrubs, with yellow fls; s.-w. Minas Gerais in the basin of Rio Grande.

    108c. var .speluncae

    2. Lfts elliptic-oblanceolate, like the branchlets and sepals glabrous; major secondary veins of lfts 8-15 pairs; procumbent subshrubs with orange or red-orange fls; Sa do Cipo and vicinity, s.-centr. Minas Gerais.

    108a. var .purpurascens

    1. Ovary and pod villosulous or setulose; known only from Sa. do Espinhapo and the lfts dorsally with axes of inflorescence and buds all at least thinly villosulous; petals always yellow.

    3. Lfts in shape, texture and venation as var. purpurascens, but dorsally pubescent above the pulvinule; ovary and pod villosulous (not setulose); fl-color, habit of growth and range of dispersal poorly known. 

    108b. var. ochnacea

    3. Lfts stiffly chartaceous, obovate, with ±5-8 pairs of more slender secondary veins camptodromous into an intramarginal one scarcely thicker; ovary and pod viscid-setulose; e. slope of s. Sa. do Espinhaço e. and s.-e. from Belo Horizonte.

    4. Stems of the year smooth except for a few minute viscid setules, fine villi lacking.

    108e. var. latifolia

    4. Stems of the year shaggy-villosulous with soft spreading-ascending villi to ±0.5 mm.

    108d. var. mollis