Acta Botanica 28. (1982)

1982 / 1-2. szám - BORHIDI ATTILA: Studies in Rondeletieae (Rubiaceae), III. The genera Rogiera and Arachnothryx

5 Acta Botanica Academiae Scientiarum Hungaricae, Vol. 28 (1-2), pp. 65-71 (1982) STUDIES IN RONDELETIEAE (RUBIACEAE) III. THE GENERA ROGIERA AND ARACHNOTHRYX A. Borhidi ECOLOGICAL AND BOTANICAL INSTITUTE OF THE HUNGARIAN ACADEMY OF SCIENCES, VÁCRÁTÓT, HUNGARY (Received: 1 January 1982) Based on a comparative study of the North American species of the genus Rendeletid, author found essential generic differences between the Antillean and Central American species. Revalidates the genera Rogiera Planch, and Arachnothryx Planch. with amplified descriptions and respective combinations. As it was pointed out (Borhidi and Fernandez 1982: 309) the original concept of Rondeletia L. has been largely widened by De Candolle (Prodr. 4: 406, 1830) and Bentham (PI. Hartw. 1841). Planchon — Flores des Serres 5: 442,1849 — recognized, that Central Amer­ican Rondeletia species had terminal paniculate and thyrsoid inflorescences and flowers with bearded or naked throat of corolla, without faucial ring, lamellae or denticles. He observed also a characteristical arachnoid pubescence on the corolla and leaves of several species. Upon these differences Planchon described two genera separated from Rondeletia L. - namely Rogiera and Arachnothryx. Later both genera have been merged into Rondeletia s.l. Rogiera was included by Bentham and Hooker (1873) and K. Schumann (1897) without any taxonomic rank. Arachno­thryx has been considered by the same authors as a section of Rondeletia. Standley in his treatment on Rondeletia (1918) created a new section for Rogiera by the name: Amoenae Standi., and divided the Arachnothryx into two new sections: Leucophyllae Standi, and Lani­­florae Standi. The mentioned authors and others dealing with American Rondeletieae, as Hemsley, Donnel-Smith, B. L. Robinson etc. paid little attention to the structure of the corolla tube and throat, considering them as features of secondary importance. In my opinion the structure of the corolla-throat is very important in taxonomical and evolutionary points of view. The structure of the throat, the presence or absence of the faucial ring, its form, pubescence, etc. have an important role in the mechanism of pollination, in the selection of the possible pollinators, in the development of basic plant-animal relationships which may be decisive in the evolution and phylogenetic relations of the different taxonomic groups. Based upon a comparative morphological examination, Borhidi and Fernandez (1982a and b) determined the chief generic characteristics of Rondeletia L. based on R. americana. Comparing these characteristics with those of other groups of Rondeletia, it turned out, that a close correlation can be found between the different forms of corolla-throat, the structures of placenta and the exine pattern and form of pollen grains. Acta Botanica Academiae Scientiarum Hungaricae 28, 1982

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