Monographs Details: Cassia gymnothyrsa H.S.Irwin & Barneby
Authors:Howard S. Irwin, Rupert C. Barneby
Authority: Irwin, Howard S. & Barneby, Rupert C. 1978. Monographic studies in Cassia (Leguminosae, Caesalpinioideae). III. Sections Absus and Grimaldia. Mem. New York Bot. Gard. 30: 1-300.
Family:Caesalpiniaceae
Description:Latin Diagnosis - Cassia gymnothyrsa Irwin & Barneby, sp. nov., habitu foliolisque parvis subrotundis multi- jugis resupinatis C. dawsonii affinis sed inflorescentia aphylla praelonga axin primarium foliatum subaequanti (6-14 nec 1.5-2.5 dm longa), foliolis ipsis majoribus (5-17 nec 2-8 mm diam), necnon floribus androecioque brevioribus abstans.

Species Description - Undershrubs with 1-few mostly simple terete brown wandlike stems arising erect from a xylopodium, at anthesis 9-20 dm, sparsely leafy in the lower 1/2-1/3, the ±5-10 cauline leaves very long and narrow and separated by long internodes, the stem (except at very base) with lf- stalks and inflorescence finely minutely pilosulous and glandular-hispidulous with weak yellow setules up to 0.3-0.5 mm, the lfts (of adult stem lvs) very numerous crowded small round concolorous glabrous, the inflorescence a long narrow few-branched and few-fld thyrsiform panicle as long or longer than the leafy stem. Stipules stiffly ascending, subulate, 1-2.5 mm persistent. Lvs ascending and divaricate 5-20 cm, heteromorphic, the lowest (often shed by anthesis) much shorter and simpler than the rest, the median and upper (as described hereafter) at least 9 cm, all petioled; pulvinus dilated at base, otherwise scarcely differentiated, up to 1.5 mm; petiole 14-27 mm, at middle 0.8-1.2 mm diam, tapering distally, 2-winged and openly grooved ventrally; rachis 7-17.5 cm; lfts 12—38., of most adult leaves at least (13-) 15 pairs, crowded along rachis, tilted adaxial margin upward on dilated when dry wrinkled pulvinule 0.4-0.6 mm, in outline broadly ovate to suborbicular, obtuse to shallowly emarginate, or obscurely deltate- apiculate, (4-)5-17(-21) x (3-)4-17(-24) mm, at base cordate on both sides but more deeply adaxially, the margins entire or obscurely crenulate, a few erratically setulose and sometimes near base minutely villous-ciliolate, the blades subcoriaceous, on both faces dull olivaceous glabrous, the midrib and 5-7 pairs of secondary veins above immersed, beneath prominulous, the midrib sharply so, a few tertiary venules sometimes faintly prominulous beneath but not forming a regular mesh. Inflorescence a narrow, strictly few-branched thyrsiform panicle of racemes (3.5-)6-14dm long, less than 1 dm diam, the axis of the individual racemes mostly 5-20-fld and including peduncle up to 2 dm, the one expanded fl raised to level of the corymbosely crowded buds; bracts submembranous, ovate or subulate, 1-1.5 mm, probably deciduous; pedicels at anthesis ascending, very slender, 2-2.5 cm, bracteolate ±4 mm below calyx; bracteoles ± 1 mm; buds ovoid apiculate, thinly pilosulous and setulose, glutinous; sepals greenish-yellow, ovate-elliptic, 8.5-11.5 x 4.5-6.2 mm, the outer acute, the inner obtuse; petals yellow, the adaxial of the four plane flabellate-cuneate ones ± 14-20 x 12-19 mm, larger than the rest, these ± 12-17 x 10-14, the fifth falcately semi-ovate, ± 15 x 7, folded back over the androecium. Pod unknown. — Collections: 2. Plate 11.

Discussion:

A remarkable virgate cassia with inflorescence surpassing surrounding herbaceous vegetation, C. gymnothyrsa is evidently related to C. dawsonii, endemic to a segment of Serra Geral do Parana a short distance to the south and like it in the multifoliolate leaves of extremely narrow outline. The leaves, however are coarser and broader, and instead of being distributed along the stems well up to and sometimes within the relatively short inflorescence as in C. dawsonii, are all borne on the lower half or third of the wandlike stem, which passes abruptly into a simple raceme or strictly few-branched panicle, including the naked common peduncle (3.5-)5-14 dm long.

Distribution:Brazil South America| Goiás Brazil South America|

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