NOTE ON POLLEN TRANSPORT, POLLINATION AND PROTECTION OF OVARIES IN FICUS SYCOMORUS*

Abstract

BY J. GALIL AND D. EISIKOWITCHDepartment of Botany, Tel Aviv University, Tel Aviv, IsraelIn previous studies on pollination and fruit setting in the sycomore fig {Ficus sycomorusL.) no satisfactory explanation had been offered for the manner of introduction of polleninto the young figs at the female phase (Galil and Eisikowitch 1968a, b). The three speciesof sycophilous wasps {Ceratosolen arabicus Mayr, C galili Wiebes and Sycophaga syco-mori L.) are not hairy and scarcely any pollen is found on the external surface of theirbodies when they penetrate into the figs. Despite this fact, one of these wasp species,namely Ceratosolen arabicus, causes abundant seed setting, whereas the other two waspspecies do not cause any setting at all. While in search for an explanation of this in-triguing phenomenon, unique pollen pockets were observed on the ventral side of themesothorax of female C. arabicus, on both isdes of the body (Plate i, Nos. i and 2). Thesepockets are roughly pear-shaped, with one or two narrow openings on both sides. Crossand longitudinal microtome sections of the insect's thorax (Plate i. No. 2) clearly showthe pollen grains within these pockets. The loading of pollen into the pockets is effectedby the already impregnated female wasps prior to emergence from their birth figs. Thusthe pollen is introduced safely into the young figs, despite the cleansing movements ofthe insect and the narrowness of the entrance slits between the ostiolar scales. The un-loading of the pockets and the ensuing pollination of the female flowers are carried outby the wasps directly, by the use of their fore-legs in the course of egg-laying. Insofaras C. galili and Sycophaga sycomori lack functional pollen pockets, introduction of polleninto the young syconia is specific for Ceratosolen arabicus, and the difference betweenthis species and the other two vis-a-vis seed production by Ficus sycomorus is thus clearlyelucidated.Observations on the behaviour of female wasps during egg laying and pollinationprovide an answer to another riddle—why syconia inhabited jointly by Ceratosolenarabicus and Sycophaga sycomori produce seeds in profusion, despite the fact thatSycophaga has a relatively long ovipositor enabling it to occupy long-styled flowers,which are generally left by Ceratosolen for seeds. Our observations have shown thatoviposition by C. arabicus takes place in well-defined areas. The wasp deposits eggsmainly into short-styled flowers, rendering the neighbouring long-styled ones unsuitablefor occupation by Sycophaga by stinging the styles and gnawing the stigmata. Conse-quently, the areas of the syconium occupied by Ceratosolen and Sycophaga respectivelyremain distinct until the final ripening. Ceratosolen areas contain abundant seeds whilethose of Sycophaga remain absolutely seedless. These findings point to the fact that thesyconium occupied by sycophilous wasps is not a homogeneous entity but is ratherdivided into distinct areas which may be small or large, depending on the nature andnumber of the wasps that had entered it at the receptive female phase. Only precise