Borreria laevis is exceedingly variable vegetatively, the leaves varying in degrees of glabrity and pubescence on the lower surface, in size and shape, the internodes short or much elongated, the stems elongate and much branched to short and/or unbranched, subsessile or petiolate, and with corollas varying from 3.5-4.5 mm long. Nevertheless, the species is at once recognizable by the characteristic pilose interior of the corolla lobes, which are generally longer than the short tube, the relatively short and broad calyx lobes, the mainly glabrate stem with fine retrorse pilosity, the puberulous or villosulous stipular sheath, and by the usually sulcate and transversely furrowed surface of the mature seeds. Although the mature seeds possess this transverse furrowed aspect, the immature or younger seeds may show only a plain surface with minute reticulation and only one or two faint transverse shallow lines or beginnings of sutures may be evident. Such is the case, for example, in Maguire, Schulz, Soderstrom & Holmgren 54185 from the Wilhelmina Gebergte of Suriname.
The type collection of Spermacoce guianensis Brem. (Rombouts 75 from Corantijne River, Wonotobo, Suriname) is matched by numerous specimens of Borreria laevis, as shown by the villosulous pubescence of the interior of the corolla lobes and the well-developed stipular sheath minutely puberulent on the outside surface. The character of the well-developed stipular sheath separates Borreria laevis at once from the species of Spermacoce (S. confusa Rendle and S. tenuior L.) found in northern South America, in which the stipular sheath is much less, if at all developed. The type collection of Spermacoce guianensis is in a comparatively young state of anthesis and does not show well-matured fruits. It does manifest the pilosulous lines on the angles of the stem as well as the filiform processes at the base of the flowers, as well as the characteristic broadly triangular, short calyx lobes of Borreria laevis.