Blütenmorphologische und palynologische Untersuchungen an Littorella

Abstract

Die unterschiedlichen Auffassungen uber den Blutenstand von Littorella und ihre verwandtschaftlichen Beziehungen zu Plantago werden diskutiert. In diesem Zusammenhang schien eine bluten- und pollenmorphologische Bearbeitung der drei Arten der Gattung nutzbringend. Eine Auswertung zahlreicher Bluten erbrachte den Beweis, das auch hier die angeblich strenge Vierzahligkeit durchbrochen wird und somit Hinweise fur eine mogliche Ableitung von einem pentameren Blutenaufbau zu finden sind. Als Pollentyp konnte ein sphaeroidaler, pantoporater Pollen erkannt werden, der sich nur wenig von dem der Hauptgattung Plantago unterscheidet. In the monograph of the Plantaginaceae by Pilger (1937) Littorella is looked upon as a genus with three species. The indigenous Littorella uniflora (L.) Aschers. — native to the Atlantic Europe — is closely related to L. americana Fern., distributed in Eastern North America. In South America there occurs the most interesting species, L. australis Griseb., in two part-areas (in Southern Chile near Panguipulli-Lake and more southern near Lake San Martin to Seno de Ultima Esperenza and on Eastern Falkland-Island). Littorella is a perennial water-or swamp plant, growing on sandy and muddy soils. It can be living submersely throughout life without flowering and propagating by runners in this case. Its occurence, the structure of its inflorescence and ovary apparently quite different and the position of the male flower gave repeatedly rise in literature to the opinion, to seperate Littorella and Plantago far from each other. Indeed, in Littorella as well as in Plantago and the third genus Bougueria, native to the Andes of Peru and Bolivia, the leaves are arranged in rosettes, but the steams are extremely compressed. In the first enumerated genera, the axillary leafless main-axis is ending into a spherical to cylindrical ear, whereas in Littorella there is only one male flower (rarely two!) at the base of which there are sitting several female ones. These different opinions on the inflorescence of Littorella and its relationships to Plantago are discussed. In this connection, a flower- and pollenmorphological elaboration of the three species of the genus seemed to be useful. An evaluation of numerous flowers furnished the proof, that, also here, the ostensibly strict fourfoldness of the corolla is broken through and thus, indications for a possible derivation from a pentamere structure of the flower are to be found.