Senna hayesiana (Britton & Rose) H.S.Irwin & Barneby

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 1: 1-454.

Family

Caesalpiniaceae

Scientific Name

Senna hayesiana (Britton & Rose) H.S.Irwin & Barneby

Type

Holotypus, NY (hb. Torr.)!—Cassia hayesiana (Britton & Rose) Standley, Contrib. Arn. Arb. 5: 75. 1933.

Synonyms

Chamaefistula hayesiana Britton & Rose, Chamaefistula maxonii Britton & Rose, Cassia maxonii (Britton & Rose) Schery, Chamaefistula hayesiana Britton & Rose, Cassia hayesiana (Britton & Rose) Standl., Chamaefistula subpilosa Britton & Rose, Chamaefistula valerioi Britton & Rose, Chamaefistula membranacea Britton & Rose, Chamaefistula williamsii Britton, Chamaefistula anconis Britton & Rose, Chamaefistula lanata Britton, Chamaefistula chiapensis Britton & Rose, Cassia brittoniana Lundell, Chamaefistula standleyi Britton & Rose, Cassia standleyi (Britton & Rose) Standl., Chamaefistula acuminata Britton & Killip, Chamaefistula subcoriacea Britton & Killip, Chamaefistula apiculata Britton & Killip, Chamaefistula deficiens Pittier

Description

Species Description - Shrubs (1-) 1.5-7 m, erect or sprawling, becoming sarmentose when support offers, and both in forest and in open places eventually arborescent to 10(-15) m with trunk up to 7 cm diam, with pliantly plagio- or geotropic hornotinous branchlets, the stems cylindric smooth or striate elenticellate, at first brown becoming grayish, the young growth except for the glabrous or remotely minutely puberulent upper face of lfts pilosulous or strigulose with fine weak hairs up to 0. l-0.45(-0.5) mm, the vesture of lfts mostly spreading (especially along major veins), rarely appressed or vestigial (exceptionally 0), that of the thyrsiform or thyrsiform-paniculate inflorescence mostly appressed, rarely loosely incurved, the thinly chartaceous or (mature) subcoriaceous lfts bicolored, olivaceous or brownish and moderately lustrous above, paler brown or subglaucous-green beneath, the mature inflorescence variable in form, the early racemes or early leafless racemiferous branchlets often axillary to lvs (therefore immersed in foliage), the lvs abruptly reduced or eliminated upward and the primary axis of the oblong or subcorymbiform panicle flexuous or zigzag. Stipules falcately linear-caudate, oblanceolate-acuminate or -acute, or sub- linear, 5-21 x 0.7-6 mm, 1-several-nerved, early caducous or deciduous before the lf. Lvs below inflorescence 6-25(-28) cm; petiole with often discolored but little swollen pulvinus (1-) 1.5-4.2(-5.5) cm, at middle 1.1-2.4(-2.8) mm diam, openly very shallowly sulcate; rachis (l-)1.5-4.4(-5) cm, a little longer or shorter than petiole; glands 1-2(-3), 1 always sessile or subsessile at proximal pair, lance- or ovate-linguiform obtuse, or horn-shaped subacute, glabrous, 1.5-4 mm tall, often 1 similar and smaller between distal pair, the seta in addition (or instead) often glandular-thickened at base with refracted setiform tail or reduced to a small gland standing behind the distal pair of pulvinules; pulvinules usually little swollen, 2-5(-6) mm; distal pair of lfts ovate-, elliptic- or obovate-acuminate 16(-18) x 2.5-8.5 cm, 1.6-2.9 times as long as wide, the acumen varying from broadly deltate to triangular-subcaudate, rarely reduced to a minute apiculus, the blade at base when relatively narrow subsymmetrically cuneate both sides, with relatively increased width more asymmetric and rounded on proximal or sometimes both sides, the margin revolute, the straight or slightly incurved midrib with 6-12(-14) major camptodrome and often several almost equally strong intercalary secondaries either finely prominulous or immersed above, or (in age) depressed-canaliculate, beneath sharply prominulous (and often discolored against a pale ground), the tertiary venules and reticulation irregular, prominulous only beneath, the ultimate sharply defined areoles either > or <1 mm diam. Peduncles both solitary and, by contraction of a common axis, appearing 2(-3) together in an axil, either ascending from ascending primary axis or refracted from pendulous one, (0.4-) 1-3.5(-4) cm; racemes densely (5-)7-30-fld, at first subcorymbose, the axis often elongating, in fruit (0.5-)l-5(-8) cm; bracts ovate or lanceolate 2-4.5(-5) mm, subherbaceous membranous-margined, usually early caducous, sometimes persistent into anthesis; pedicels of fertile fls (caveat: apparently open fls may be quite immature and short-pedicellate) 18-40(-46) mm; buds when very young ovate obtuse, thinly strigulose, opening to expose the androecium long before true anthesis, becoming just before anthesis oblong- ovoid; sepals submembranous, little graduated, the inner ones up to (4-)4.5- 7(-7.5) mm; petals usually dull, sometimes golden yellow, pubescent dorsally glabrous within, subhomomorphic except the adaxial one often a trifle wider, seldom much expanded, all short-clawed, at full anthesis normally becoming 11-19(-22) mm, sometimes many failing to expand and reaching 8-11 mm, then more densely hairy dorsally; functional androecium 4-merous, the 3 adaxial and 3 abaxial stamens reduced to staminodes or obsolete, the filaments glabrous 1-2(-2.5) mm, the 4 thecae homomorphic, almost straight or gently incurved (5.5-)6-8.5(-9) mm, glabrous or randomly puberulent in the dorsoventral grooves, the very short 2-porose abruptly divaricate beak 0.3-0.7 mm; ovary densely whitish-pilosulous, the short glabrescent incurved style little dilated, 0.6-0.9(-1.1) mm diam, the stigmatic cavity 0.4-0.7 mm diam; ovules 128-192. Pod pendulous stipitate, the stipe 2-6 mm, often scarcely longer than diam, cuneately dilated into the body, this narrowly cylindroid obtusangulate, straight or slightly decurved, terete unless constricted by atrophy of ovules, (6.5-) 10-24 x 0.8-1.3 cm, the ventral suture 1-2.5 mm wide bordered on either side by a thickening of the valve wall 1.5-3 mm wide, the valves firm, subcoriaceous green becoming brown, smooth or faintly venulose, early glabrate; dehiscence along ventral suture, follicular, the endocarp finally separating as a continuous ribbon; seeds 2-seriate transverse, turned broadside to the septa and embedded in black pulp, compressed-ovoid or obliquely ellipsoid, 3.9-5 x 2.7-3.5 mm, the testa mahogany-brown, brilliantly lustrous, cross-crackled, exareolate.— Collections: 321.

Distribution and Ecology - Wet evergreen and seasonally dry semideciduous woodland, usually in open sunny places along streams, in stony glades, and in forest-savanna ecotone, in Panama and Costa Rica coming out into beach-scrub along the Ocean, in cleared and disturbed forest persisting in thickets and becoming weedy in hedges and neglected pasture, mostly 5-750 m, but recorded from Chiapas up to 1060, from Guatemala to 1200, from El Salvador to 1230, from Honduras to 1300, from Costa Rica to 1130, from Panama (Chiriquf) to 1300 and from Venezuela to 1800 m, widespread from s.-e. Mexico (on Gulf slope from e. Oaxaca to Campeche, on Pacific slope from Istmo de Tehuantepec to highland Chiapas) s.-e. through Central America (all states) to Panama (all departments), thence more rarely e. through lower Cauca and Magdalena valleys and Sa. Nevada de Santa Marta in n. Colombia e. to the upper Rio Meta on the Boyaca-Meta boundary and to the Maracaibo slope of Cordillera de Merida in adjacent Venezuela; cultivated and reported naturalized on Martinique in West Indies.—Fl. abundantly VIII-I, sporadically through the year.

Discussion

The senna which we describe under the name S. hayesiana, common through out much of Central America below 18°N and especially abundant in Panama, is in great part that which Bentham (1871, p. 521, t. 61) had in as Cassia oxyphylla, though not the genuine C. oxyphylla Kunth and never fully extricated from C. bacillaris. It is distinguished from these, as from all sympatric quadrifoil sennas and indeed from all other Bacillares by its functionally tetramerous androecium, from which not only the three adaxial, but also the three, usually heteromorphic abaxial members are suppressed or reduced to rudiments, leaving four stout straight or only slightly incurved anthers erect, parallel to each other, on very short filaments. This columnar androecium determines the shape of the mature corolla which forms around it a campanulate sheath of loosely appressed petals, perceptibly different from the expanded, bowl-shaped flower of S. bacillaris or S. fruticosa. The pod, finely illustrated in Bentham s plate of C. oxyphylla, which we conjecture to be drawn from a Panamanian collection (Fendler 88, K), is essentially that of S. bacillaris in form, texture and dehiscence, so that fruiting specimens are only with difficulty separated by the less oblique, less intricately venulose leaflets unless, as in Fendler 88 (but unfortunately not consistently), the seta terminating the leaf-stalk is transmuted into a gland, a feature foreign to S. bacillaris. Material of S. hayesiana at Kew annotated before 1871 by Bentham as Cassia oxyphylla includes good tetramerous flowers collected in Mexico by Jurgensen, Liebmann, and E. P. Johnson, in Nicaragua by Oersted, and in Panama by Sutton Hayes, but Bentham made no mention of the androecium. In his monograph (1871, p. 522) he contradictorily cited several of these specimens as a possible variety of C. bacillaris differing in their broader, more densely pubescent leaves, but at the same time "evidently nearly allied to C. oxyphylla." The species was first fully and correctly diagnosed and characterized by Schery (1951, p. 77) under the technically superfluous name C. maxonii, superfluous because a prior C. hayesiana, obligatory in the circumstances, was overlooked. In extricating the tetramerous C. hayesiana from sympatric heptamerous allies, Schery was able to reduce four Brittonian segregates to one superficially variable entity. Pursuing the same course outside of Panama, we are now obliged to list as synonyms no less than thirteen names proposed by Britton and colleagues together with one of Pittier from Venezuela and the relatively early (but homonymous) C. inaequilatera Ram. Goy. The chamaefistulas are mentioned below in relation to internal variation in C. hayesiana. In spite of the elaborate synonymy which suggests the contrary, S. hayesiana is not by any means an exceptionally polymorphic senna. Stature of the plant covers a range from a low sprawling shrub to a small forest tree, but this range is common to most Bacillares. The vesture of young branchlets and foliage varies (as described above) in density, length and orientation. Young leaves and shade leaves are submembranous, whereas older ones or those borne in the canopy tend to be firmer, sometimes bullate by depression of the secondary and subsequent venulation. The leaflets vary in outline, relatively narrow ones tending to be drawn out into acuminate or even caudate tips, whereas broader ones are more abruptly narrowed into a triangular or deltate point. The normal, fully developed inflorescence is an exserted panicle of racemes, sometimes leafy at the base but leafless distally; but especially out of season, or early in the season of normal bloom, some random racemes are often borne solitary in axils of mature leaves. The floral bracts, ordinarily caducous, occasionally persist into full anthesis. The perianth varies considerably in size, but care must be taken to distinguish between flowers at full anthesis and those which, despite exserted androecia which give an impression of maturity, are in reality not fully blown. The androecium itself is the most stable feature of the species, varying little in size or proportions. The variation on these lines recorded from our now very ample sample of S. hayesiana is readily accommodated in one species, showing no internal correlations and no perceptible geographic pattern. The segregates listed in our synonymy exhibit these particular character-combinations: Chamaefistula valerioi (Costa Rica): average in all respects for the species. Ch. chiapensis (Mexico) and Ch. standleyi (Costa Rica): as Ch. valerioi except for somewhat emphasized and subpersistent stipules and bracts. The difference in flower-size claimed in Britton & Rose’s key (1930, p. 232) is illusory. Ch. lanata (El Salvador): exactly = Ch. valerioi except for immature panicle, most flowers yet unexpanded and the petals consequently appearing more densely pubescent dorsally. The typus is of interest because it includes thick-textured, incipiently bullate leaflets and thin-textured, finely reticulate ones, ostensibly from one tree. Ch. membranacea (El Salvador): based on a poorly pressed, insect-ravaged specimen with relatively thin-textured leaflets. Ch. subpilosa (El Salvador): based on a specimen bearing only the small leaves normally present at base of the terminal panicle. Ch. maxonii (Panama): exhibits the state of flowering out of season (May 28), with few, few-flowered racemes axillary to ample cauline leaves. Ch. hayesiana (Panama): the typus closely resembles that of Ch. membranacea except for subappressed vesture of lower leaf-face; it has no fully expanded flowers. Ch. williamsii and Ch. anconis (both Panama): normal Panamanian C. hayesiana in mature fruit. Ch. acuminata and Ch. apiculata (both from Medellin, Colombia): leaflets thinly strigulose, not pilosulous, beneath, in the first subcaudately acuminate, in the second proportionately broader and abruptly contracted at apex into a small point. Ch. subcoriacea (Colombia): leaflets intermediate in outline between those of the two last mentioned, but densely villosulous beneath. Ch. deficiens (Venezuela): leaflets in outline as the preceding, but almost glabrous beneath; petals poorly developed.

Distribution

Chiapas Mexico North America| Chiriquí Panamá Central America| Oaxaca Mexico North America| Campeche Mexico North America| Boyacá Colombia South America| Meta Colombia South America| Martinique South America| Belize Central America| Guatemala Central America| Honduras Central America| El Salvador Central America| Nicaragua Central America| Costa Rica South America| Panama Central America|