Reproductive Structures and Evolution in Ludwigia (Onagraceae). II. Fruit and Seed

Ludwigia seed coats cut in various ways and examined with light microscope and w SEM have four similar cell layers regardless of wire: noteworthy modifications E. only in taxa with seeds fused to the fruit wall.Surface features of the seeds are also much alike except Ge Microcarpium, a diverse section in which some of the species deviate with respect to the orientation of epidermal cells.In sections Ludwigia, EE and : : rone ER Keys for identifying the species of Ludwigia usually begin with stamen number, a legacy from Linnaeus.Distinguishing features of greater evolutionary importance, however, are the uniseriate or pluriseriate arrangement of ovules and the presence or absence of persistent endocarp tissue around mature seeds.Illustrations of uniseriate and pluriseriate ovules accompanying the section on placentation in an earlier article ( Eyde, 1977); I continue here with the anatomy of the seed coats and the fruit.Corners (1976) observations and illustrations of Ludwigia ("Jussieua") peruviana have aided me; not so the earlier literature.Ohlendorf (1907) could see only one cell layer in a tegmen that is really 2-layered.Rode (1913) saw one layer too many in the testa.Van Wisselingh's (1920) description and sketch, which reappeared in Netolitzky's (1926) compilation, are accurate, but brief; moreover, one cannot tell what ludwigia van Wisselingh or Rode worked with.Rode's "spindelformig" seeds were supposed to be those of Jussieua angustifolia.This name is a synonym of L. octovalvis, however, and the seeds of L. octovalvis are not spindle shaped.Van Wisselingh identified his material as L. mullertii hort., à name now applied to a seedless plant (Mühlberg, 1972).My observations are taken from vouchered material prepared in a number 1I thank D. Dille, T. P. Geier and P.