Shrubs up to 3 meters high; stems glabrous below, the upper por- tions puberulous, the hairs upwardly curved, up to 0.13 mm. long; leaf blades oblong, up to 19 cm. long and 9 cm. wide, short-acuminate (the tip itself rounded), narrowed at base and decurrent on the petiole, moderately firm, entire, both surfaces glabrous or the lower minutely and sparingly puberulous on costa, cystoliths obscure and scattered; petioles up to 1 cm. long (including the wing at the base of the blade, this 6 to 7 mm. wide), minutely puberulous with upwardly curved hairs; racemes solitary, terminal, narrow and lax, the flower- bearing portion about 9 cm. long and 8 mm. broad, the peduncle 4 cm. long, the lowermost internode of the raceme 2 cm. long, the others successively shorter toward tip of inflorescence, both peduncle and rachis rather densely and minutely hirtellous with both glandular and acute hairs, these spreading or ascending and up to 0.25 mm. long; bracts (the lower pair without flowers) lanceolate, slenderly acute, the larger ones 4 mm. long and about 0.75 mm. wide at base, minutely hirtellous with a mixture of more or less spreading glandular and acute hairs; bractlets ovate to lanceolate, 2 mm. long, 0.75 mm. wide at base, acute, rather sparingly and minutely hirtellous; pedicels
rather stout, up to 2.5 mm. long, rather densely hirtellous with minute glandular and acute hairs; calyx segments narrowly lanceolate, 6.5 mm. long, 0.75 mm. wide at base, narrowed to a slender acute tip, minutely and more or less densely hirtellous with glandular and acute hairs; corolla not seen (greenish yellow, García-Barriga); capsules minutely hirtellous with glandular and acute, spreading or ascending hairs (up to 0.16 mm. long), the solid stipe about 1.5 cm. long, 2 mm. broad, curved after dehiscence, the seed-bearing tip (4-seeded) 12 mm. long, 8 mm. broad, 3 mm. thick, subacute; seed brownish-purple, flattened, suborbicular, 4 mm. broad and long, 2 mm. thick, coarsely wrinkled, the wrinkles more pronounced toward margins of seed.
Type in the U. S. National Herbarium, No. 2144877, collected in Caño Unguyá, at Jino-Gojé, between the Ríos Piraparaná and Popeyaká, tributaries of Río Apaporis, Amazonas-Vaupés, Colombia, 250 meters altitude, September 3-11, 1952, by H. García-Barriga (No. 14377).
In many respects Pseuderanthemum galbanum resembles P. poecilanthum; the inflorescence, the shape and size of the bracts. and bractlets, and the pubescence of the two species are practically identical. There are, however, several striking differences. P. poecilanthum is herbaceous, rarely if ever exceeding 30 cm. in height, the leaves are relatively smaller, and the flowers white with conspicu- ously purple-spotted lobes. In contrast, P. galbanum is a shrub or small tree as much as 3 meters high; its leaves are relatively larger, and the corollas are greenish yellow. It is to the color of the corolla that the specific epithet, galbanum, alludes.