Cassia swartzioides

Title

Cassia swartzioides

Authors

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Cassia swartzioides Ducke

Description

4.  Cassia swartzioides Ducke, Archiv. Jard. Bot. Rio de Jan. 5: 129. 1930, sensu ampliato.—Typus infra sub var. swartzioide indicatur.

Trees 8-20 m with trunk attaining 4 dm diam, the annotinous and older branchlets fuscous, obtusely angulate by livid or blackish ribs descending from each lf- scar, the young branchlets and lower face of the ample chartaceous lfts with axes of inflorescence and calyx at first densely, later more thinly puberulous with fine sinuous or straightish subappressed hairs 0.1-0.25 mm, the foliage bicolored, the lfts when dry brownish-olivaceous and lustrous above, paler dull beneath, sharply reticulate-venulose on both faces, the solitary, paired or rarely paniculate racemes stiffly ascending from nodular spurs on old wood below the current foliage or from temporarily leafless annotinous branchlets.

Stipules linear-subulate 0.8-1.4 mm, caducous from the incipiently expanding lf, absent from mature foliage.

Adult lvs 1.5-3.3 dm; petiole including livid pulvinus (2-)2.5-4.5(-6) cm, openly shallowly sulcate ventrally; rachis (6-)7-19 cm, its longer interfoliolar segments (1.5-)2.5-4(-5) cm; pulvinules 3.5-4.5 mm; lfts (3-)4-7 pairs, accrescent distally, the ultimate pair broadly elliptic or ovate-elliptic obtuse or shortly bluntly acuminate 8-14 x 2.5-6(-7) cm, (1.9-)2-2.8 times as long as wide, at subequilateral base rounded or broadly cuneate, the margin strongly or obscurely revolute, the midrib depressed on upper and cariniform on lower face, the 10-21 major camptodrome and usually many intercalary secondary veins prominulous on both faces, a close tertiary and subsequent venulation sharply raised on upper face and equally or sometimes more faintly so beneath.

Racemes sessile or almost so, 15-45-fld, the young fl-buds crowded into a narrow cone above the expanded fls, the axis elongating, becoming 8-18 cm; bracts and bracteoles firm, broadly ovate 2.5^ mm, densely gray-puberulent on both faces, caducous as the pedicel begins to elongate; pedicels at full anthesis 1-3 cm; sepals greenish or fuscous obovate subequal, densely puberulent both within and without, 7.5-10.5 mm, all early reflexed; fls fragrant, the petals either homochromous or the pandurate vexillary one heterochromous, the shape and coloring described under the vars.; the longest petal 15-21 mm; androecium glabrous except for dorsally puberulent anthers, the 3 sigmoid, distally dilated long filaments 20-30 mm, the 2 between them erect 7-9 mm, the 3 adaxial antepetalous ones dilated 5-7 x 1-1.4 mm, the 2 between these 1.5-3.5 mm; anthers of 3 long abaxial stamens 2-3.8 x 1.7-2 mm, those of the 5 antepetalous ones diminishing toward the vexillum all resupinate 2.2-2.9 mm, those of 2 adaxial antesepalous ones substerile 0.65-1.1 mm diam; ovary densely gray-strigulose; style very short, the minute stigmatic orifice introrsely terminal; ovules 70-110.

Pod (of var. scarlatina, even this little known) pendulous cylindric a trifle laterally compressed 40-70 x 2.5 cm, bluntly carinate by sutures ±5 mm wide, the ultimately woody valves fuscous rough, transversely fissured and ±1 mm thick at maturity, the cavity divided by stiffly chartaceous septa ±6-7 mm apart; seeds (not seen ripe) turned broadside to the septa, suspended in pulp.

In habit, foliage, inflorescence, fragrance, and what is known of its ecology, C. swartzioides closely resembles C. spruceana, from which it differs chiefly in the heteromorphic vexillary petal and the color of the rest. The vexillum takes the form of a pandurately oblanceolate blade constricted toward the base and, between this constriction and the short claw, dilated on each side into a flabellate lobe irregularly crenulate around the margin. The lateral and abaxial petals are not different from those of C. spruceana; they vary from oblanceolate to oblong- obovate, sometimes (especially the 1-3 adaxial) minutely angulate-appendaged at the claw. There are two color patterns in the flower of C. swartzioides for which Ducke proposed specific status. In the commoner var. scarlatina all petals open vivid brick-red, blood-red, or pinkish-orange, or the banner may open yellowish and fade to red in age. In var. swartzioides the yellow element in the pigment is suppressed but some red persists, the vexillum remaining rose-tinted in contrast with white lateral and abaxial petals. Despite Ducke’s insistence on the importance of flower-color in this group, we are at a loss for characters of substance to support the differences in pigmentation, obviously capable in this group of canafistulas of somewhat capricious changes (see note under C. cowanii). The relatively rare pink and white var. swartzioides replaces var. scarlatina, so far as known, only in a restricted enclave on the Peruvian Amazon near Iquitos, within the range of var. scarlatina which is found along the great river both up- and downstream. The petals of both varieties turn brownish-yellow or livid when dried, and are then indistinguishable unless the coloration has been recorded in vivo. Imperfect small flowers that open but fail to expand either corolla or androecium are known in both color-forms of C. swartzioides. A tree of var. scarlatina from near the type-locality (Krukoff 9107, NY) had nothing but these depauperate flowers, whereas a collection of var. swartzioides (Schunke 30, NY) has a few such mixed in the same panicle of racemes with amply expanded flowers.