L[ntroduction 
The Myrsinaceae are almost exclusively tropical woody plants. The family 
is difficult, for there are few bold characters with which to separate genera and 
species. Classification must be based on the interpretation of variable morpho- 
logical characteristics. Problems of relationships are perplexing, and fine dis- 
tinctions are necessary to bring any order out of chaos. Anyone not willing to 
accept fine morphological distinctions should not venture into the taxonomy of 
the Myrsinaceae. 
The most important treatment of the family is the monograph by Dr. Carl 
Mez which was published in 1902 in Das Pflanzenreich.! This is outdated and 
no longer satisfactory, but it is still the basic reference work. Earlier treatises 
were by Alphonse DeCandolle, of which the most important is in the Prodromus.” 
Parathesis Hook.f.’ is one of the well-marked natural genera. Aside from Mez’s 
monograph, the only definitive treatment of the genus is by Lundell in the Flora 
of Guatemala,* which covers the species of a limited geographical area. Strictly 
American, it can be distinguished easily by its pubescent flowers, narrow sepals 
open in bud, and valvate petals which are papillose-tomentose within. 
Indicative of the problems encountered in the Myrsinaceae, the number and 
arrangement of the ovules in the placenta have been used to separate the tribes 
and genera. Yet the study of Parathesis has revealed that such distinctions can 
be used only with reservation. Ovule number in Parathesis ranges from three in 
P. tenuis Stand]. to nineteen in P. trichogyne Hemsl., the former uniseriate, the 
latter pluriseriate. In other species some of the ovules are biseriate. Formerly 
this genus was considered to have few uniseriate ovules, and placed in the 
Tribe Myrsineae! In spite of these variations within a single genus, the number 
of ovules and their arrangement still must be considered basic in making tribal 
and generic distinctions. Such is the nature of the Myrsinaceae. 
The monograph of Parathesis is based on accumulated collections in major 
herbaria of America and Europe. Types, isotypes and authentic specimens of 
every species, excepting P. Rothschuhiana Mez, have been studied. The identity 
of P. Rothschuhiana is quite well established from the photograph of the type 
and drawings by Mez. 
The only excluded binomial is P. acutissima Cuatr. (Rev. Acad. Colomb. 
Ciene. 8: 324. 1951), a taxon with broad imbricate sepals. Known only from 
fruiting material, its generic position is uncertain. 
The study of herbarium collections has been implemented by field investiga- 
1 Mez, Carl, Myrsinaceae. In A. Engler, Das Pflanzenreich IV. 236: 1-437, figs. 1-61. 1902. 
2 Candolle, Alphonse De. Myrsinaceae. In DC. Prodr. 8: 75-140. 1844. 
’ Hooker, J. D. In Benth. & Hook. f., Gen. Pl. 2: 645. 1876. 
4 Lundell, Cyrus Longworth. Fieldiana: Bot. 24, Part 8: 160-189, figs. 43-52. 1966. 
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