Senna marilandica

  • Title

    Senna marilandica

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna marilandica (L.) Link

  • Description

    142.  Senna marilandica (Linnaeus) Link, Handbuch 2: 140 ("marylandica"). 1831, based on Cassia marilandica Linnaeus, Sp. PI. 378. 1753.— "Habitat in Virginia, Marilandia."—Lectoholotypus (Fernald, Rhodora 39: 410, pi. 480. 1937): LINN 528.27!—Cassia acuminata Moench, Meth. 273. 1794 (exclus. descr.), nom. substit. illegit. C. reflexa Salisbury, Prod. 326. 1796, nom. substit. illegit. Senna riparia Rafinesque, Medical Fl. 1: 94. 1828, nom. substit. provis. Ditremexa marilandica (Linnaeus) Britton & Rose, N. Amer. Fl. 23(4): 257. 1930, quoad nom., exclus. descr.

    Cassia succedanea Bellardi ex DeCandolle, Prod. 2: 498, pro syn. 1825.

    Cassia medsgeri Shafer, Torreya 4: 179, fig. 2 (a-d). 1904.—"PENNSYLVANIA: . . . Westmoreland Co., 1904, O. P. Medsger (type) . . ."—Holotypus, collected in South Huntingdon Township, 12.VIII (fl) & X (fr) 1904, NY!—Ditremexa medsgeri (Shafer) Britton & Rose, N. Amer. Fl. 23(4): 257. 1930.—Equated with C. marilandica by Fernald, 1937, lc.

    Ditremexa nashii Britton & Rose, N. Amer. Fl. 23(4): 258. 1930.—"Swamp near Eustis, Lake County, Florida, August 16-25, 1894, George V. Nash 1720 "—Holotypus, NY!—Equated with C. marilandica by Isely, 1975, pp. 112, 212.

    Cassia marilandica sensu Bentham, 1871, p. 534 & auct. antecedent, ex parte, exclus. S. hebecarpa; Deam, Fl. Indiana 589, map 1200. 1940; Fernald, 1950, p. 886; Gleason, 1952, p. 384 + fig.; B. L. Turner, 1959, p. 75, map 38; Stevens, Kansas Wild Fls, ed. 2, 263, figs. 438-440. 1961; Gleason & Cronquist, Man. Vase. Pl. N.-e. U.S. 397. 1963; Wilbur, 1963, p. 25, fig. 7; Radford et al., Man. Vase. Fl. Carolinas 576 + fig., map. 1964; Rickett, Wild Fls U.S. 2: 320, pl. 116. 1967; Wharton & Barbour, Wildfls Kentucky 211 + fig. 1971; Isely, 1975, p. 110, map 48, p. 205 (where lectotypus erroneously numbered LINN 528.16); McGregor & Barkley, Atlas Great Plains Fl. map 622. 1977.

    Cassia medsgeri sensu Britton & Brown, Ill. Fl. ed. 2, 2: 336. 1913; Rydberg, Fl. Prairies Plains N. Amer. 450. 1932.

    Coarse, amply leafy perennial herbs, at maturity (6-)7-14(-20) dm, the several-many stems erect and narrowly ascending in clumps from a blackish pluricipital horizontal rootstock, appearing glabrous but the stems distally, lf-stalks, axes of inflorescence and commonly the margins of lfts thinly or remotely pilosulous with subappressed or incurved hairs up to 0.2-0.5(-0.6) mm, the foliage bicolored, the thin-textured lfts dull olivaceous above, paler subglaucescent beneath, the inflorescence a narrow thyrse of racemes proximally subtended by scarcely diminished lvs, these often abruptly smaller upward and the thyrse then exserted in age.

    Stipules ascending or weakly deflexed, thinly herbaceous, narrowly lanceolate 5-9 x 0.5-1.4 mm, caducous, absent from mature spms.

    Major lvs 12-24(-27) cm; petiole including little modified, sometimes livid pulvinus (2-)3-7(-8) cm, at middle 1.3-2 mm diam, coarsely ribbed dorsally and laterally, openly shallow-sulcate ventrally; gland situated next to pulvinus or on petiole proper distant up to 16(-20) mm from stem, exceptionally between proximal pair of lfts, sessile or substipitate, in outline ovoid, globose, depressed- globose or oblong-fusiform, in profile (1-) 1.2-2 x 0.6-1.7 mm, the body commonly broadest at or below middle; rachis 6.5-16(-17.5) cm; pulvinules 1.6-2.6(-3) mm; lfts (5-)6-9 pairs, accrescent distally but the penultimate sometimes longest, all in outline elliptic, oblong-elliptic or lanceolate acute or obtuse mucronate, the small proximal ones often ovate-elliptic, the longer ones (3-)3. 5-6 x 0.9-2. l(-2.4) cm, 2.5-4(-4.3) times as long as wide, at base rounded or cordate on proximal and cuneate on distal side, the margins plane or incipiently revolute toward the pulvinule, the straight midrib immersed or almost so above, cariniform beneath, the 8-12 pairs of slender camptodrome secondary veins above either faintly prominulous, immersed or finely impressed, beneath finely prominulous, the reticular venules invisible above, commonly discolored dorsally but not raised.

    Racemes (3-)5-15(-19)-fld, the axis including peduncle becoming (0.4-)0.7-4(-4.5) cm; bracts membranous-margined, lanceolate or lance-attenuate (2-)2.5-4 mm, caducous; mature pedicels 9-15(-17) mm; fl-buds nodding, glabrous except for minutely ciliolate sepal-margins; sepals moderately graduated, pinkish- brown pallid-margined, ovate or oblong-obovate obtuse, the outer (4-)4.5-5.7 mm, the inner 5.5-7.5(-8.5) mm; petals glabrous, yellow drying whitish brown-veined, of subequal length 8-13(-14) mm, the vexillar one obovate-emarginate, the rest broadly oblanceolate or cuneate-oblanceolate obtuse; androecium glabrous, the staminodes 1.2-1.4 mm wide, the filaments of 4 median stamens 2-3.5 mm, of 2 longer abaxial ones greatly dilated 4-7.5 mm, of the centric abaxial one 2.6-5.5 mm, the anthers livid, those of 4 median stamens 2.6-3.5 mm, almost straight, obscurely 2-lipped, those of 2 long, lunately incurved abaxial ones measured from obtuse base to shortly 2-lipped orifice 4-5 x 1.3-1.5 mm, the pollen- cup very short and not appendaged ±0.3 mm, the centric abaxial anther similar but a little shorter and only 0.6-0.75 mm diam; ovary strigulose or pilosulous, the hairs up to 0.2-0.5 mm; style commonly ±2, sometimes up to 4 mm, gently incurved but scarcely dilated distally, 0.2-0.4 mm diam at the lateral stigmatic cavity; ovules 20-26(-28).

    Pod gently curved out- and downward from ascending pedicel, the stipe 1-2.5 mm, the body linear compressed (6.5-)7-9.5(- 11) x (0.75-)0.8-1.05(-1.1) cm, the valves at first green or reddish, when ripe papery nigrescent glabrate or remotely strigulose, alternately more and less deeply depressed-sulcate at successive interseminal septa, the seed-locules 3-4 mm long, thus oblong and much shorter than wide; seeds perpendicular to the pod’s long axis, plumply obovoid or oblong- obovoid compressed parallel to the valves 3.9-5.1 x 2.2-3 mm, the testa light ocher-brown sometimes castaneous-tinged, dull or sublustrous, crackled, the obovate areole 2.7-3.5 x 1.3-2 mm; n = 14 (Irwin, 1960).—Collections: 64.

    Open woodland, alluvia of valley floors, creek-banks, swamps and moist thickets, sometimes colonial in old pastures where shunned by livestock, widespread and locally plentiful over Alleghanian, Ozarkian and mid-western United States from s.-e. Nebraska to Pennsylvania, s. to n.-e. Texas, Alabama, and through montane and piedmont Carolinas and Georgia to middle Florida.—Fl. VII-IX.

    Although the sibling species, S. marilandica and S. hebecarpa, were both cultivated in western Europe in early XVIII century, they were not recognized as distinct for two hundred years. They are indeed extraordinarily similar in habit and floral structure, and are sometimes even now difficult to distinguish at anthesis, however sharply marked they may become as the pod and seeds develop. Following Fernald’s critical analysis of the morphology and nomenclature (1937, l.c.), exaggerated reliance has been placed on the shape of the petiolar gland and on pubescence as differential characters, with the result that some small errors have crept into the record of dispersal. While the gland of S. hebecarpa is commonly shortly stipitate and claviform and that of S. marilandica is most often sessile and ovoid or mounded, there is much variation in both species and some glands cannot be referred with confidence to either type. The setose cauline vesture of S. hebecarpa, commonly coinciding with a shaggy-pilose ovary, is sometimes very sparse and in southeastern New York and New Jersey is often entirely lacking; flowering plants from this region with glabrous stems and merely strigulose-pilosulous ovaries have been misidentified as S. marilandica, the range of which does not extend east of Pennsylvania. In doubtful cases a count of the ovules, 10-16 in S. hebecarpa and 20-28 in S. marilandica, is decisive. Isely (1975, l.c.) mentions specimens that suggested "limited introgression" between S. marilandica and S. hebecarpa, but despite their essentially identical flowers and wide (although incomplete) sympatry, we find no evidence to confirm the presence of gene flow between them.

    Collectively S. marilandica and S. hebecarpa represent a specialized offshoot of the genus adapted to temperate summer climate and resistant in the winter- dormant state to zero temperatures. Of the two, S. marilandica appears the less advanced or modified, its relatively numerous ovules and more southern (but still entirely extratropical) range suggesting more immediate kinship to tropical antecedents. The differences between the pair in the pod and seeds can be visualized as all contingent on reduced ovule-number in S. hebecarpa: in a pod of unaltered length fewer ovules occupy longer cavities and develop into broader, more strongly compressed seeds over which the pod-valves become less convexly elevated. Similar but not identical reciprocal adjustments between more and less crowded seeds are described under S. hirsuta. In that species, however, the pod varies greatly in length, and it is length, not ovule-number, that determines the outline of the individual seed-locule and consequently the orientation and compression of the seed itself.

    Senna ligustrina, vicariant with S. marilandica southward in Florida from about 28°30'N, differs in its slender acute petiolar glands, lance-ovate rather than oblong-elliptic leaflets, corymbose rather than thyrsoid inflorescence, and in its obliquely ascending rather than declined, pluri (36-50, not 20-28)-ovulate pods.

    This species was first described by Linnaeus in Hortus Cliffortianus, and specimens survive in the Clifford Herbarium (BM) as: Cassia No. 8 = Senna occidentalis foliis ebuli acutis, glabris; misplaced as one of 4 sheets of Cassia No. 7; detached flowers mixed with sterile Chamaecrista nictitans as Cassia No. 1.