Brachyotum rostratum (Naudin) Triana
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Authority
Wurdack, John J. 1953. A revision of the genus Brachyotum (Tibouchineae-Melastomataceae). Mem. New York Bot. Gard. 8 (4): 343-407.
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Family
Melastomataceae
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Scientific Name
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Description
Species Description - Trichomes minutely and moderately roughened. Branchlets obscurely quadrangular, densely to moderately fine-hirsute to strigose or strigulose, the hairs mostly eglandular, occasionally with some intermingled gland-tipped hairs. Petiole 1-6 mm. Blade (5-)10-25 x (2-)5-13 mm., ovate to elliptic or oblong-elliptic with the apex bluntly acute or rounded and the base obtuse to truncate, the 3 primaries narrowly impressed above and elevated below, the 8-15 pairs of secondaries above obscurely impressed or obsolete and below narrowly elevated but mostly obscured by the pubescence; above moderately short- (rarely long-) strigose, the hairs 2-5(-8)/mm.a on low callosities and in 10 or more irregular rows with the adherent expanded bases O.2-O.5(-1.5) mm. diam. and the more or less abruptly attenuate free apices (0.2-)0.5-1(-3) mm. long; below densely to very densely loose-strigulose to fine-hirsutulous, the hairs (10-)15-30/mm.2 and mostly eglandular but occasionally with intermingled gland-tipped hairs, the glands solitary and dense (15-60/mm.2) but obscured by the trichomes. Flowers predominantly 5-merous, mostly ternate (rarely a few solitary) or sometimes with an additional pair of flowers at the node below the dichasial node or the dichasia ternate. Peduncle of dichasium (5-)10-25 mm. long and slender (about 1/2-2/3 diam. of the supporting branchlet); bracts at base of the dichasium 3-10 x 1-4 mm., persistent until anthesis, with pubescence as in leaves or above glabrous. Pedicels 0.5-7 mm. below bracteoles, 1-7 mm. above; pedicellar bracteoles 1.5-6 x 0.3-2 mm., mostly caducous before anthesis, above glabrous or apically strigulose, below moderately loose-strigulose. Hypanthium 4-8 x 4-6 mm., 0.2-0.5 mm. thick raedianly, sparsely to moderately strigulose or appressed-hirsutulous, the fine hairs 6-12(-15)/mm.2 and eglandular or in part gland-tipped. Sepals 4-7 x 3-4.5 mm., narrowly oblong-ovate to triangular-ovate with the apices acute, united at bases 0.6-1 mm., the sinuses rounded-acute. Petals yellowish (or purple fide Naudin), 9-16 x 8-12 mm., asymmetrically obovate with the apices obliquely truncate, outside glabrous or very sparsely strigulose at base and apex, the glandtipped cilia 0.1-0.5 mm. Filaments 3.5-7.5 mm.; anthers 4-6.5 mm.; connective at anther base not prolonged (rarely free of anther 0.15 mm. or less). Style 15-20 x 0.5-0.7 mm., exserted 4-8 mm. Ovary 4=7 x 2.5—3.5 mm., moderately strigulose on the apical 2-3 mm., usually the hairs in part gland-tipped, the apical lobes 0.1-0.3 mm. above the locules.
Distribution and Ecology - Distribution: north central to southeastern Peru, alt. 3100-4100 m.
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Discussion
Chaetogastra rostrata Naudin, Ann. Sci. Nat. III. 14: 135. 1850.
Ckaetogastra microphylla Naudin, Ann. Sci. Nat. III. 14: 136. 1850.
Brachyotum microphyllum (Naud.) Triana, Trans. Linn. Soc. 28: 49. 1871. Non sensu Cogniaux; DC. Monog. Phan. 7: 164. 1891.
Brachyotum trianaei Cogniaux, DC. Monog. Phan. 7: 167. 1891.
Brachyotum callosum Macbride, Field Mus. Pub. Bot. 4: 172. 1929.
Type Collection and Locality: Dombey s.n. (HOLOTYPE presumably at P; isotypes BM, BR, F, G-DEL, L, P, US); "Peruvia," probably in Depts. Huanuco, Pasco, or Junin.
Type Photographs: F38256 (isotype of B. rostratum at P); Gleason 27-12 and F16718 (destroyed isotype of B. rostratum at B); F36133 (holotype of B. microphyllum at P); Gleason 51-4 (isotype of B. trianaei, at G-DC ?); F16719 (destroyed isotype of B. trianaei at B); F63423 (holotype of B. callosum at F).
Vernacular Name: Pinchos (Ochoa 206).
Of the 141 examinable flowers in the various collections ascribed to this species, all except 20 were 5-merous. All except 6 of the 39 examinable flowers of Lecbler 2061 were 5-merous, although B. trianaei was described as 4-merous.
The degree of distinctness of this complex from B. lutescens is dubious; some specimens vary toward B. lutescens and some toward B. rosmarinifolium. The interplay of appressed and patent stem pubescence and glandular and non-glandular stem, lower leaf surface, and hypanthial trichomes certainly permits no specific distinctions between the species synonymized under B. rostratum. "Typical" B. trianaei (B. callosum) has spreading to appressed stem pubescence, loosely appressed to spreading lower leaf surface hairs, and appressed to loosely appressed hypanthial hairs, all such hairs being eglandular except for a very few of the sinusal ones; such collections are Isern 583, Lechler 2061, Macbride & Featherstone 2181, Metcalf 30548, Raimondi 9439, and Stork & Horton 10429. Dombey s.n. and Ferreyra 7504 have very long, dense, spreading to loosely appressed stem hairs, with gland-tipped ones more or less abundantly intermingled with the non-glandular on the stems, lower leaf surfaces, and hypanthia; the leaves are ovate to ovate-elliptic. Asplund 11900, Ochoa 206, Pennell 13847a, Soukup 387, and Vargas 2057 have mostly lanceolate to oblong leaves which have nonglandular hairs beneath (except Asplund 11900) and many of the hypanthial hairs gland-tipped; the style of Vargas 2057 is very sparsely beset with stout spreading hairs on the basal %. In B. microphyllum, the young leaves on the flowering branches are elliptic to oblong, but the leaves on vegetative shoots are ovate; the hairs on the upper leaf surfaces have exceptionally well-developed calloused bases; only a very few stem hairs, the petal cilia, and the young ovary hairs are gland-tipped; such collections are Bonpland s.n. and Sandeman 4118. Except for the greater pubescence density and longer free apices on the upper leaf surface hairs, these two specimens resemble the "trianaei" element, having similar scanty development of gland-tipped hairs.
Jameson s.n. (K), from Pillzhum in Ecuador, resembles B. rostratum in its ternate 5-merous flowers with glandular hypanthia, but the leaves are much less pubescent beneath than usual and the connective is free of the anther base 0.2 mm.; further collections are needed to establish the status of this specimen.