Psychotria nitidella M.-Arg., Mart. Fl. Bras. 6(5): 250. 1881.
Color notes concerning the inflorescence branches and corolla vary greatly. The main axes of the inflorescence may be green, vermilion, red, or orange-red, while the corolla is described as red, yellow, scarlet with pale-flesh and whitish apex, salmon with paler yellow or cream or whitish lobes, and variations of these.
Palicourea laevigata H. & B., described from the Río Atabapo, Amazonas, Venezuela, may be synonymous with Palicourea nitidella, at least in part as represented by the fragmentary upper branch on the photo of the Humboldt & Bonpland 996 specimen. This photo shows a leaf having an obtuse or rounded apex and with 13-18 horizontally spreading lateral nerves, the leaves being 5.5-11 cm broad; those on the upper detached branch are narrower, 5.5-6.5 cm broad, with 13-15 lateral nerves on each side, while the other two detached leaves on the remainder of the sheet are larger and broader, 11 cm broad and with 17 or 18 lateral nerves on each side. The two detached larger leaves of the specimen shown in the type photograph resemble those of P. grandifolia var sprucei (Nonatelia macrophylla H.B.K.), but that has pubescent lower leaf surfaces, midrib, and nerves. The photo of Psychotria laevigata has “no. 996” and “Rio Atabapo” written at the top of the original label below the two larger leaves above referred to, but another label has been placed under the top detached branch with “Nonatelia grandiflora H.B.K." written on it. Two different species may be represented, P. nitidella being possibly identified with the upper fragmentary branch, and P. grandifolia var sprucei being likely identified for the lower two detached leaves. Under the circumstances, it seems wiser to reject Palicourea laevigata as a nomen confusum, based on two different elements.
Palicourea nitidella and P. grandiflora often are found in the same locality. The two taxa may be distinguished by the narrower corollas of P. grandiflora with sparser and more minute external puberulence, a looser and more elongated type of inflorescence in P. grandiflora with the branches more widely separated, a glabrous hypanthium in P. grandiflora, more densely puberulent hypanthium in P. nitidella, a glabrous or glabrate rachis and peduncle of the inflorescence in P. grandiflora with only sparsely minutely puberulent pedicels, whereas in P. nitidella the peduncle is minutely puberulous and all the branches are densely puberulent, and finally in P. grandiflora the calyx is glabrate or remotely and sparsely minutely puberulent with short hairs on margins, whereas in P. nitidella the pubescence of the calyx is denser and the margins are more densely ciliolate.