Senna pneumatica

Title

Senna pneumatica

Authors

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Senna pneumatica H.S.Irwin & Barneby

Description

105.  Senna pneumatica Irwin & Barneby, sp. nov., ut videtur S. organensi (Harms) proxime affinis, imprimis ab ea leguminis longioris pro rata angustioris 6-10 x 0.8-1.1 (nec 3-6.5 x 1.1-1.7) cm valvulis elevatim reticulatis necnon seminibus opacis ad hilum corneis, ulterius a var. organensi (in monte Caparao sub sympatrica) glandula petiolari solitaria (nec inter omnia paria) petiolisque brevioribus 0.8-1.7 (nec 1.5-3) cm longis diversa.—MINAS GERAIS/ESPIRITO SANTO: Sa. do Caparao, 2200 m, 30.IX.1941 (fl, fr), A. C. Brade 17052.—Holotypus, RB 45970; isotypus, NY.

Slender erect shrubs ±1 m, the angulately ribbed stems naked after 1 season, densely leafy and paniculately branched distally, the lf-stalks and margins of lfts thinly subappressed-pilosulous with mostly straight lustrous hairs up to 0.3-0.6 mm, the foliage subbicolored, the (dry) lfts brownish-green, a little paler beneath, the few-fld axillary racemes immersed in lvs.

Stipules thinly herbaceous, early dry caducous, lance-acuminate or ovate-ellip tic acute ±5-7 x 1.2-3.5 mm.

Lvs 3-6.5 cm; petiole including livid pulvinus 8-17 mm, at middle 0.4-0.6 mm diam, shallowly sulcate; rachis 1.5-3.5 cm; gland between proximal pair stipitate, in profile 1.5-3 mm tall, the ovoid-acuminate body 0.5-0.9 mm diam, commonly sigmoidally incurved; pulvinules 0.8-1.2 mm; lfts 5-9 pairs, a trifle accrescent upward, broadly oblanceolate or oblong-obovate obtuse, minutely mucronulate (6-)10-16 x (2.5-)3-5.5 mm, 2.4-3 times as long as wide, at slightly asymmetric base cuneate or rounded on both sides, the margin plane, the centric midrib immersed above, carinate beneath, the (4-)5-7 pairs of camptodrome secondary veins visible only beneath, there discolored but not prominulous.

Peduncles 2-2.5 cm; racemes ±2- 12-fid, the axis ±0.5-2 cm; bracts (caducous, little known) resembling stipules in shape and size; pedicels (4-)8-18 mm; fl-buds plumply oblong-obovoid glabrous; sepals livid except for pallid membranous margins, broadly elliptic obtuse, little graduated, the inner ones ±4.5-5.5 mm; petals glabrous, yellow fading pale with dark venation, of subequal length, the banner cuneately flabellate, the rest broadly oblanceolate or obovate beyond the claw, the longest ±7.5-8.5 mm; androecium glabrous, the filaments of 4 median stamens 1.5-2 mm, of 3 abaxial ones ±3 mm, the anthers of 4 median stamens nearly straight 2.6-3.2 mm, of 3 abaxial ones slightly incurved 3.7-4 mm, all abruptly truncate at apex; ovary loosely pilosulous; style dilated, at apex ±0.2 mm diam; ovules ±10.

Pod obliquely ascending, the stipe 4-5 mm, the narrowly oblong body (4.5-)6-10 x 0.8-1.1 cm, piano-compressed, keeled by the slender cordlike sutures, the chartaceous brown valves scarcely elevated over seeds, sharply transversely venulose-reticulate, the intraseminal septa 0.2-0.4 mm wide, 4-7 mm apart; seeds compressed-obovoid or oblong-obovoid ±6.5-7.2 x 3.4-4 mm, the testa dull castaneous, corneously thickened around hilum, exareolate.—Collection: 1.

Habitat not recorded, to be expected in stony campo or about outcrops near 2200 m, known only from upper slopes of Sa. do Caparao on the Minas Gerais-Espirito Santo boundary.—Fl. IX-X(-?).

This still poorly known senna is certainly related to S. organensis, which it resembles in habit, form of stipule, foliage, perianth and androecium, at the same time differing, so far as we can tell at present, in the absolutely and proportionately longer, sharply reticulate-venulose pod and in the dull seed-testa corneously thickened around the hilum. It is more easily and directly separable from var. organensis, which occurs at the same elevations on Sa. do Caparao, in the single gland on the leaf-stalk and in the plane-margined leaflets. However solitary glands and plane leaflet-margins are encountered in some distantly allopatric varieties of S. organensis sens. lat. and we depend for specific distinctions on the pod and seed.