1953] 



REVISION OF BRACHYOTUM 



385 



26. Brachyotum cernuum (Bonpl.) Triana, Trans. Linn. Soc. 28: 48. 1871. 

 Rhexia cemua Bonpl. Rhexies 32. 1806-1808. 



Osbekia cemua (Bonpl.) Sprengel, Syst. Veg. ed. 16. 2: 312. 1825. 

 Chaetogastra cemua (Bonpl.) DC. Prodr. 3: 135. 1828. 



Trichoraes smooth, slender. Branchlets notably quadrangular, very sparsely 

 strigulose, soon glabrescent except on the angles, the nodes conspicuously an- 

 nular-setose, these hairs to 5 mm. long. Petiole 3-6 mm. Blade 18-30 x 8-15 mm., 

 ovate with the apex bluntly acute and the base broadly obtuse to truncate, the 3 

 primaries impressed above and strongly elevated below, with an additional faintly 

 developed pair of marginals, the secondaries forming a prominent reticulum which 

 is obscurely impressed above and narrowly elevated below; above glabrous; be- 

 low sparsely short-strigose on the primaries, with only a few scattered hairs and 

 a few scattered inconspicuous clumps of glands on the surface. Flowers con- 

 stantly 5-merous, ternate or with an additional pair at the node below the di- 

 chasial node, the dichasium compact and its peduncle not differentiated nor pen- 

 dent, the persistent leaves subtending the dichasium only slightly reduced. Pedi- 

 cel 1-7 mm. below the bracts, 2-4 mm. above; pedicellar bracts persistent, 6- 

 8 x 1-2 mm., or those subtending the center flower of the dichasium leaflike. Hy- 

 panthium 4-5 x 4 mm., 0.2 mm. thick medianly, glabrous to very sparsely strigu- 

 lose, the hairs fewer than 2/mm. 2 Sepals 9-13 x 2.5-4 mm., lanceolate with nar- 

 rowly acute apices, glabrous except for the marginal appressed cilia and a few 

 appressed hairs abaxially along the midveins, united at bases about 1 mm., the 

 sinuses acute. Petals deep purple, 13-18 x 10-15 mm., rhomboidal-obovate and 

 symmetrical with the apices narrowly obtuse, the non-glandular cilia 0.2-0.8 mm. 

 Filaments 4.5-6 mm.; anthers 4-5 mm.; connective at anther base 1.3-1.7 mm., 

 free of the anther 0.7-0.9 mm., the ventral lobing 0.7-1 mm. Style 19-26 x 0.7-0.8 

 mm., exserted 7-10 mm. Ovary 4-4.5 x 3.5-4 mm., moderately long-strigulose on 

 the apical 1-2 mm., the apical lobes 0.2-0.3 mm. above the locules. 



Type Collection and Locality: Bonpland s.n. (HOLOTYPE presumably in 

 Herb. Humboldt & Bonpland at P; isotypes F, P); Colombia, Dept. Cauca, "(Monte 

 de Purase), juxta urbem Popayan . . . plus de 2000 metres." 



Type Photographs and Illustrations: F36137 (presumed holotype); Rhexies pi. 

 13 (1806-1808) (as Rhexia cernua). Triana's illustration (Trans. Linn. Soc. 28: 

 pi. 3, /. 33b. 1871) is probably not this species, since the flower shown there is 

 4-merous and with a quite pubescent hypanthium. 



Distribution: southern Colombia, alt. 2000-3200 m. 



Cauca: between Chapa and Rio Blanco, Core 907 (NA, NY). Narino: Tuquerres and 

 Almaguer, T-iana s.n. (BR, K, NY, P, US, W); Volcan de El Galeras, Ewan 16332 (NY). 

 Without Department: Hartweg 1003 p.p. (P, S, W). 



Hartweg 1003, from the various labels seen, was collected in various locali- 

 ties, Pichincha, Pasto, and Popayan being cited on the diverse specimens; the 

 specimens cited for B. cernuum are probably from one of the latter two locations. 



All of the 42 examinable flowers in the various collections were 5-merous. 

 This species is strikingly like the Bolivian specimens of B. grisebachii, being 

 distinguishable only by the much sparser hypanthial pubescence, 5*merous flow- 

 ers, more symmetrical petals, much less dense abaxial leaf surface pubescence, 

 and shorter apical ovary lobes. However, the closest relative of B. cernuum seems 

 to be B. lindenii, which differs in the drooping dichasial peduncles, early-cadu- 

 cous pedicellar bracteoles, rounded to broadly obtuse petals, inconspicuously 

 developed nodal setae, usually smaller leaves, and denser hypanthial pubescence. 



Ewan noted on his collection of B. cernuum that it appeared to be a lower- 

 altitude relative of his collection of B. lindenii (Ewan 16330). The logical mor- 



