Borreria ocimoides f. bisepala (Bremek.) Steyerm.
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Authority
Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
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Family
Rubiaceae
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Scientific Name
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Discussion
Borreria ocimoides var bisepala Brem., Rec. Trav. Bot. Néerl. 31: 307. 1934.
Bremekamp differentiated this variation by its possession of only two calyx lobes, instead of four, and additionally described the plants “on the whole smaller and frailer, and with somewhat broader leaves. The flowers are also smaller than in the type.” The characters mentioned by Bremekamp, such as size of plant, width of leaves, and smaller flowers, do not correlate with the presence of or the number of calyx lobes. Plants with two calyx lobes occur within the range of the typical four-lobed plants, and at the most can be considered only a mere form. The Spruce 2374 has two calyx lobes.
The specimen of Schomburgk 394, isotype of Mitrocarpum puberulum Benth, so far as the sheet at NY is concerned, is conspecific with Borreria ocimoides; it has stems with pilose angles, leaves sparsely pilose above with subappressed hairs, and glabrous below except for the sparsely short puberulous midrib, lateral nerves faint and three to four on each side, four calyx lobes, 0.4-0.5 mm long in anthesis, and scarious white-margined and serrulate on margins. The isotype sheet at US of Schomburgk 394, on the other hand, is a Mitrocarpus, apparently identical with M. diffusus.
Borreria ocimoides is frequently confused with Mitracarpus diffusus, M. villosus, and Spermacoce confusa. It is separated from these taxa on fruiting characters, and, in addition, from Spermacoce confusa it differs in the glabrous to sparsely pilose or short puberulous instead of conspicuously densely rough scabrous upper leaf surface, the abundance of hyaline filiform bracteoles among the heads and stipular sheaths, and in the less prominently hispidulous ciliate and narrower calyx lobes. From the two species of Mitracarpus mentioned, Borreria ocimoides shows the following differences: the calyx lobes are less elongated with shorter cilia, the leaf margins are less conspicuously scabrous, the pubescence of the stems is much less developed in Borreria ocimoides, whereas in Mitracarpus diffusus the stems are densely short puberulous throughout and in M. villosus they are spreading-pilose with elongate hairs, in Mitracarpus taxa the stems are subterete, whereas in Borreria ocimoides the stems are 4-angled and slightly winged, and, finally, in Mitracarpus diffusus the leaves are densely short pubescent above and even more pubescent beneath, whereas in Borreria ocimoides the leaves are much less pubescent, more often glabrous to sparsely puberulous.