Senna stipulacea

  • Title

    Senna stipulacea

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna stipulacea (Aiton) H.S.Irwin & Barneby

  • Description

    109.  Senna stipulacea (Aiton) Irwin & Barneby, comb. nov. Cassia stipulacea Aiton, Hort. Kew. 2: 52. 1789.—Typus sub. var. stipulacea infra in- dicatur.

    Cassia opaca N. Graham, Edinburgh New Philosoph. J. 4: 173. 1828.—"We received a plant from Raith this season, it having been raised by Mr. Ferguson’s Gardener from South American seeds, communicated by Professor Leslie in 1825."—No typus seen, but the description, especially of the stipules, strongly suggesting S. stipulacea sens, lat., the precise variety indeterminable.—Equated with C. stipulacea by Bentham, 1871, p. 538, who cited the name ex Vogel (1837, p. 42), having been misled by Vogel’s erroneous reference to vol. 2 (not 4) of the Edinburgh Journal into thinking C. opaca unpublished by Graham.

    Amply leafy shrubs of bushy habit, at anthesis 1-3.5 m, the young stems, lf- stalks and axes of inflorescence remotely, sparsely, or sometimes densely pilosulous with pale lustrous spreading or procumbent hairs to ±0.3-0.9 mm, the malodorous foliage either membranous dark green or firmer and pallidly olivaceous, the lfts bicolored, paler beneath, their revolute margins ciliolate but their faces either both glabrous or the ventral one puberulent along the depressed midrib and the dorsal one sometimes remotely pilosulous, the racemes axillary to and shorter than developed lvs, all lateral or finally crowded into a small leafy- bracteate panicle.

    Stipules erect foliaceous, resembling lfts in texture and venation, in outline rhombic, ovate- or obovate-cuneate, or broadly elliptic-oblanceolate (3-)5-17(- 19) x (2-)4- 10(-13) mm, 1.1-2.2 times as long as wide, acuminate or abruptly acuminulate at apex, at base broadly or narrowly cuneate, deciduous before the lf.

    Lvs (6-)7-17 cm; petiole including discolored but little-swollen pulvinus (10-) 12-35 mm, at middle (0.6-)0.7-1.4 mm diam, the ventral sulcus usually narrow or closed, sometimes open and shallow; rachis 4-12 cm; glands l(-2) between proximal and often 1 between second (third) pair of lfts, stipitate or subsessile, in profile 1-2.8 mm tall, the lance ellipsoid or plumply ovoid-acuminate, straight or porrectly clawlike head 0.4-0.9 (rarely vermiform and only 0.1-0.2 mm diam; pulvinules 1-2(-2.6) mm; lfts 4-8(-9, commonly 5-7) pairs, ± decrescent proximally but the longest pair either terminal or subterminal, all in outline subsymmetrically ovate, lanceolate or lance-elliptic obtuse or obtusely acuminulate (2-)2.5-5(-5.5) x (0.8-)0.9-2.2 cm, 2-3(-3.7) times as long as wide, at base sub- equilaterally rounded or broadly cuneate, the slender midrib sulcate ventrally, cariniform dorsally, giving rise to 6-12 pairs of camptodrome secondary veins, these variably branched and variably prominulous (see key to vars.).

    Racemes loosely 6-25-fld, the several simultaneously expanded fls not or just raised to level of unopened buds, the axis with peduncle together becoming 6-13(-16) cm; bracts thinly herbaceous, rhombic-elliptic, elliptic-oblanceolate, ovate-acuminate or obovate-cuneate, at apex commonly short-acuminate, (4.5-)5-9(-10) x (1.8-)2-5(-6) cm, deciduous well before, at, or soon after anthesis; pedicels 1-2(-2.3) cm; fl-buds subglobose glabrous or almost so; sepals petaloid, yellow or the outermost brown-tinged, obovate or oblong-obovate little graduated, (4.5-)5-7 mm; petals glabrous deep yellow or orange, subheteromorphic, the vexillary one broadly obovate-flabellate emarginate, the 2 lateral similar but obtuse, the 2 abaxial obovate-oblanceolate, the longest petal 8-11.5 mm; androecium glabrous, the conspicuous obcordate staminodes 2-3 x 1.3-1.8 mm, the filaments of 4 median stamens 1.2-3 mm, of 2 latero-abaxial ones 2-5 mm, of the centric abaxial one 1.8-3 mm, the anthers of 4 median stamens 2.6-3.5 mm, of 2 latero-abaxial ones (3-)3.3-4 mm, of the centric abaxial one ±2.3-3.3 mm but as wide as its neighbors, all biporose at apex; ovary thinly pilosulous or subglabrous; style 1.2-2.5 mm filiform, at very apex abruptly incurved and 0.1-0.15 mm diam; ovules 5-12.

    Pod obliquely pendulous, the stipe (1.5-)2-3.5 mm, the broadly oblong, strongly compressed body 2.5-5 x 1.1-1.8 cm, except when some ovules abort abruptly truncate-rounded at both ends, the stiffly papery brownish, finely intricately venulose valves early glabrate, weakly mounded over the seeds, the septa almost obsolete; seeds plumply oblong-obovoid a little compressed parallel to the valves 6.5-9 x 4.5-6.6 mm, the atrocastaneous lustrous testa smooth or microscopically pitted, exareolate.

    The mayu, a shrubby senna of the Pacific foothills and coast range of central Chile, is readily recognized in its region by the dilated stipules, equivalently enlarged floral bracts and broad short planocompressed pod. Among sympatric sennas S. cruckshanksii alone has a similar pod, but commonplace narrow bracts and stipules. We readily adopt Bentham’s concept of S. stipulacea, as expressed by specimens so annotated at Kew, but find that the species consists of two races clearly differentiated by morphology and dispersal, separable as follows:

    Key to Varieties of S. stipulacea

    1. Secondary venation of lfts immersed on upper face, on lower face simply or almost simply penniveined, tertiary venulation subobsolete; ovules 8-12; Nuble to Valdivia, ±36-40°S.

    109a. var. stipulacea (p. 336).

    1. Secondary venation of lfts prominulous on both faces and giving rise to delicately raised tertiary connecting or reticular venulation; ovules 5-7; Valparaiso and Coquimbo, lat. 34° n.-ward.

    109b. var. anglorum (p. 336).