Monographs Details: Platygyne
Authority: Liogier, Alain H. 1971. Novitates Antillanae. IV. Mem. New York Bot. Gard. 21: 107-157.
Scientific Name:Platygyne
Description:Species Description - Inflorescence monoecious, stamens 5-14, filaments not connate, on a receptacle hairy or glabrous; styles wide, emarginate at the apex; disk absent.


While collecting in the northern hills of the Dominican Republic, I found a vine that to me looked like a species of Platygyne, a genus heretofore endemic to Cuba. In trying to name it I noticed that Tragia biflora Urban corresponded to m y specimens, and that it was indeed the correct name. I then studied the differences between Tragia and Platygyne. It is indeed very difficult to tell one genus from the other.

Several species of Tragia have been reported from the West Indies. The ubiquitous T. volubilis L. being the most widespread; Cuba has two more species of very restricted endemism, T. cubensis Urban (Fedde Repert. 28: 226. 1930) and T. gracilis Grisebach (Nachr. Ges. Wiss. Goett. 1865: 176. 1865), this last species known only from the type collection. In 1928, Urban described Tragia biflora [Ark. Bot. 22A(8): 62. 1928] from Haiti, the type specimen coming from Massif de la Hotte, in the southern peninsula. Several other collections seem to extend the range; Ekman collected it again in the Dominican Republic, near Sosua on the northern coast, and I found it in the same region at El Choco, E of Sosua, where it is called Guao because of the painfully stinging hairs on the leaves and stems.

Pflanzenreich [IV. 147. IX-XI(68): 1919] Pax and Hoffmann note the following differences between Tragia Linnaeus and Platygyne Mercier: the number of stamens, the shape of the receptacle (globose or flat). According to Pax, Tragia has 3 (2 or 1 by abortion) stamens, but some species have from 30 to 50; the filaments are short, broad and more or less united at the base, which is true only for a few species, and the receptacle is flat. Platygyne, according to the definition, has a globose, hairy receptacle, fewer (5-10) stamens and the filaments are slender and attached separately to the receptacle; many of these characters are quite inconsistent, when the number of stamens is considered, the presence or absence of a receptacle, the length and width of the filaments, the shape of the styles; all these characteristics seem to be quite variable.

Platygyne was segregated from Tragia by Mercier in 1830, based on Cuban specimens. The major differences seem to be in the number of stamens, the presence of a hairy receptacle, the wider and emarginate styles. While studying the genus for the Flora of Cuba, I found that besides the very common Cuban species P. hexandra (Jacq.) Muell.-Arg., there was another described species, P. volubilis Howard (Jour. Arnold Arb. 28: 120. 1947). Studying the material collected in Cuba, I described three new species: P. leonis, P. dentata and P parvifolia (Contr. Ocas. Mus. La Salle 11: 6-8. 1952). All except P parvifolia have a hairy receptacle and 5-10 stamens; P. parvifolia has 10-14 stamens on a glabrous receptacle; this last species extends the generic concept and suggests a link between Tragia and Platygyne. Can Platygyne be kept as a different genus?

In describing Tragia biflora. Urban noted the presence in the [male] flower of a glabrous globose receptacle with up to 20 stamens; m y collection has only 10 stamens. The wide but not emarginate styles point more toward Platygyne than toward Tragia, indicating that the generic characters are intermixed. This proves that the genus Platygyne cannot be kept separate from Tragia, and I here merge the two genera under Tragia.

The following changes are then made necessary:

Tragia dentata (Alain) Alain, comb. nov.

Platygyne dentata Alain, Contr. Ocas. Mus. La Salle 11:6. 1952.

Tragia howardi Alain, nom. nov.

Platygyne volubilis Howard, Jour. Arnold Arb. 28: 121. 1947, non Tragia volubilis Linnaeus.

Tragia leonis (Alain) Alain, comb. nov.

Platygyne leonis Alain, Contr. Ocas. Mus. La Salle 11: 6. 1952.

Tragia parvifolia (Alain) Alain, comb. nov.

Platygyne parvifolia Alain, Contr. Ocas. Mus. La Salle 11: 8. 1952.