LINDLEYANA l WWW.AOS.ORG SEPTEMBER 2006 ORCHIDS 677 CAPILLITIAL EXTRUSION FROM FRUITS OF MAXILLARIA NARDOIDES (ORCHIDACEAE: MAXILLARIINAE) 1 MARIO A. BLANCO 2 , W. MARK WHITTEN 3 , NORRIS H. WILLIAMS 3 AND SAMANTHA KOEHLER 4 ABSTRACT: The fruits of Maxillaria nardoides are fusiform, 1–1.2 × 0.3 cm. Upon dehiscence, six valves separate completely at the apex, and a long cylindric mass (up to 6.5 cm long × 3 mm in diameter) of white hygroscopic trichomes (elaters) is extruded along with the seeds. This capillitium hangs limply from the fruit with its base clamped by the three placentiferous valves that fold longitudinally upon dehiscence. The seeds are forcefully ejected from the capillitium as the elaters unwind and recoil. This long extrudable capillitium appears to be unique among the Orchidaceae. Its potential adaptive value is discussed. “THE STRUCTURE OF orchid fruits has been neglected by botanists.” With these words, Robert Dressler opened his review of orchid fruits in his seminal book on orchid biology, The Orchids: Natural History and Classification (Dressler, 198l:68). There are several reasons for this neglect. First, the basic structure (ground plan) of orchid fruits is uniform, almost monotonous: the ovary is always inferior (all the floral organs are inserted at the apex of the ovary), composed of three carpels with a single locule (three-locular in a few genera; e.g., Phragmipedium, Selenipedium, Eriaxis , Clematepistephium, Palmorchis, Apostasia, Neuwiedia) and dehisces at maturity to release thousands of tiny seeds (a fissuricidal capsule sensu Spjut, 1994). This makes orchid fruits less fascinating than the flowers that produce them, and less diverse in structure than the fruits of many other plant groups. Second, orchid fruits provide few characters for identification purposes (due in part to our lack of knowledge of their detailed structure and to the traditional emphasis on floral characters). Many herbarium specimens that bear only fruits are difficult, if not impossible, to identify to species level with certainty. Third, most taxonomists do not even consider the fruits in species descriptions. A notable exception is Hallé (1977, 1986), who illustrated the fruits for many New Caledonian orchid species and emphasized their distinguishing features. Dressler (1981), Rasmussen (1985), Arditti (1992), Brieger, Maatsch and Senghas (1992), Cribb (1999) and especially Veyret (2001) summarized the scant information on orchid fruit structure. Horowitz (1902) presented a good overview of the ovary and fruit anatomy of orchids and described the fruits of many genera (regrettably with very few illustrations), but his work was not cited in any of the above-mentioned reviews. An excellent treatment on orchid fruits (Rasmussen and Johansen, 2006) appeared while the present article was in press. We completely agree with their structural interpretations (the “split-carpel model”), versus the six-carpel model favored by Veyret (2001). A closer examination of orchid fruits reveals many interesting variations in size, shape, texture and dehiscence mode. They range from a few millimeters in diameter to heavy structures many centimeters long, and from globose to long and narrow. In some cases, the pedicel elongates during fruit 2 Department of Botany, University of Florida, 220 Bartram Hall, Gainesville, FL 32611-8526, USA; and Research Associate, Jardín Botánico Lankester, Universidad de Costa Rica, Apdo. 1031-7050 Cartago, Costa Rica (mblanco@flmnh.ufl.edu) 3 Florida Museum of Natural History, University of Florida, Dickinson Hall, Gainesville, FL 32611-7800, USA (Whitten: whitten@flmnh.ufl.edu; Williams: orchid@flmnh.ufl.edu) 4 Departamento de Botânica, Instituto de Biologia, Universidade Estadual de Campinas, Caixa Postal 6109, Campinas, SP 13083-970, Brazil (samantha.koehler@gmail.com) 1 We thank the Portilla family and the staff at Ecuagenera Ltd. for giving us unrestricted access to their orchid collections in Gualaceo and El Pangui, for their hospitality, and for facilitating our research in every possible way. Vouchers of Maxillaria nardoides are deposited in the Herbaria of the Pontificia Universidad Católica de Quito (QCA) and the Florida Museum of Natural History (FLAS). Plants were collected under the permit No. 016-IC-FLO-DBAP- MA from the Ministerio del Ambiente of Ecuador. We thank Lorena Endara for assistance with permits and fieldwork, and Barbara Carlsward for lab assistance and discussions on morphology. Funding was provided by a Furniss Foundation graduate student fellowship from the American Orchid Society to M. A. Blanco, a Prance Fellowship in Neotropical Botany from the Royal Botanical Gardens Kew to S. Koehler, and the U.S. National Science Foundation grant No. DEB-234064 to N. H. Williams and W. M. Whitten for the project Systematics of Maxillariinae (Orchidaceae): generic delimitation, pollinator rewards, and pollination. LINDLEYANA l WWW.AOS.ORG SEPTEMBER 2006 ORCHIDS 677