Monographs Details: Borreria verticillata (L.) G.Mey.
Authority: Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.

Spermacoce verticillata Linnaeus, Sp. Pl. 102. 1753.

Borreria podocephala DC. Prodr. 4: 542. 1830.

The typical form of the species, based by Linnaeus upon Spermacoce verticillis globosis of Dillen. (Hort. Elth. 369. pl. 277, f. 358. 1732), and typified by specimens collected from Jamaica, has the main cauline leaves lance-elliptic to linear-lanceolate, tapering at both ends and broadest in the middle, glabrous except for minute, appressed, stiffish hairs on the revolute margins and lower midrib, and about 4 to 5 times longer than broad, varying from 2-6 × (0.2-)0.5-1.2 cm, with 2-3 very faint or obsolescent pairs of lateral nerves. Occurring with the typical form or in populations by itself is a more narrow-leaved form with most or all of the leaves numerous and linear, and varying from 1-4.5 × 0.1-0.2 (-0.4) cm. It appears frequently to be a form of the plant in which the main leaves, which are usually broader, have disappeared, leaving the subsidiary or accessory, narrower, axillary leaves remaining on the stem. For this reason, it is not given separate formal status. Of the specimens above cited, those from the Guianas and Brazil may be referred to the narrower-leaved form, whereas those from Venezuela are found throughout that country, except for specimens from Estado Bolivar, which represent the typical broader-leaved form of the species.

Borreria verticillata is often confused with glabrous, narrow-leaved growth forms of B. capitata var capitata, var tenella, and var suaveolens, and of B. oligodonta. It may be distinguished from B. capitata varieties by the smaller heads of flowers, smaller bristles of the stipular sheaths, the number (two) and shorter length of the calyx lobes, the differently shaped corolla with the relative proportions of corolla tube to lobes, the more sparsely puberulent hypanthium, and much shorter fruiting cocci. From B. oligodonta it is distinguished by the usually longer bracts subtending the flowering heads, the more even-surfaced flowering heads, the shorter corolla and lobes, and the mainly longer and broader leaves. A specimen in the Paris herbarium (Bonpland 55), labelled “Borreria atourensis Cham. & Schl.,” is a misidentified specimen of B. verticillata and does not represent Spermacoce aturensis H.B.K., which is synonymous with Borreria capitata var tenella.