Monographs Details: Mitracarpus villosus (Sw.) Cham. & Schltdl.
Authority: Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
Family:Rubiaceae
Discussion:

Spermacoce villosa Sw., Prodr. Veg. Ind. Occ. 29. 1788.

Spermacoce hirta of authors, not L.

Mitracarpum rude Benth. in Hook., Jour. Bot. 3: 238. 1841.

Lasser 566 from La Mucuy, Edo. Merida, Venezuela, is a good match for Schomburgk 409 (type collection of Mitracarpum rude Benth.) with spreading hirsute pubescence of the stems and with the leaves densely strigillose-hirsutulous on both sides with the midrib beneath covered with longer, spreading hairs.

Spermacoce hirta L., as represented in the Linnaean Herbarium, indicated on microcard as “125 Spermacoce 4 hirta,” is not the same taxon as that known as Mitracarpus villosus (Sw.) Cham. & Schl., but rather is a species of Borreria similar to B. laevis. This is supported by the following evidence from a study of the Linnaean specimen: (1) The Linnaean Spermacoce hirta has definitely long-petiolate leaves with the blades contracted to a definite petiole instead of sessile as in Mitracarpus villosus; although Linnaeus describes the leaves as sessile, the leaves are petiolate; (2) the leaves of Spermacoce hirta L. are definitely thinner than those of Mitracarpus villosus, and with manifest lateral nerves and finer tertiary venation between the nerves, whereas in Mitracarpus villosus no lateral nerves or venation is apparent on the thicker leaves; (3) in Spermacoce hirta L. the setae of the stipular sheath are prominent, whereas in Mitracarpus villosus they are much shorter and less prominent; (4) the inflorescences of Spermacoce hirta L. are quite small in comparison with the more enlarged and conspicuous ones of Mitracarpus villosus.

Swartz (Obs. Bot. 45. 1791) noted under Spermacoce hirta that the epithet of Linnaeus had been confused with another species, i e Spermacoce villosa of Swartz, the latter distinguishable from S. hirta by the included instead of exserted stamens, simpler instead of branched stems, and villous instead of scabrous pubescence of the stem.

Although a discrepancy exists in Linnaeus’s description of the leaves as sessile, it is obvious, after an examination of the Linnaean specimen, that Spermacoce hirta L. is a different taxon than Mitracarpus villosus. Fawcett & Rendle (Fl. Jam. 7(5): 127. 1936) correctly took up the latter name for the Jamaican species. Standley, on the other hand, and other authors have incorrectly used the name, Mitracarpus hirtus (L.) DC., based on Spermacoce hirta L., for the same taxon. Jacquin’s plate 308 of his Ic. Pl. Rar. 2. shows a corolla with the anthers only slightly exserted above the orifice, and not quite reaching half the length of the corolla lobes, and the two larger calyx lobes are conspicuously setulose-hispid, while the two shorter and smaller ones are about 1/3-1/4 the length of the larger calyx lobes. This is more or less the same floral details as are found in Jamaican material of Mitracarpus villosus, such as Britton 1707 from the vicinity of Kingston, in which the anthers slightly protrude above the orifice but are not exserted more than to the middle of the corolla lobes and not beyond them; in the Jamaican specimen the two shorter calyx lobes are 1.5 mm long, while the two longer ones are 2-2.2 mm long with conspicuously setulose margins. The Venezuelan and British Guianan specimens cited above match the Jamaican material whence the specimen from which Swartz described his Spermacoce villosa.