“…However, duckweeds have not yet been used to any great extent as subjeets for ultrastructural studies. In recent years there have been brief descriptions of the fine structure of Wotffia arrhiza (Anderson, Thotnpson & Swader, 1973) and Eemna perpusitta (Chiu & Falk, 1975), and a more detailed investigation into the development of sieve elements in the root of L, minor (Melaragno & Walsh, 1976), The other existing ultrastruetural investigations on tnembers of the Lemnaeeae deal with chloroplast differentiation (Le Pabic, 1972, 1976, changes in chloroplast structure as a result of various treatments (Gtob & Rufener, 1969;Porath & Ben-Shaul, 1971;Grob & Eichenberger, 1973;De Kock, Vaughan & Hall, 1978), the presence of plastids in root cells (Kawamatu, 1967;Mollenhauer, 1967;Wroblewski, 1973), and the structure of callus cells (Pan & Chen, 1976), Spirodela polyrrhiza is the largest member of the Letnnaceae and is interesting in that it forms tnodified dormant buds or turions under a variety of cotiditions (Jacobs, 1947;Henssen, 1954;Czopek, 1959), S. polyrrhiza also forms turions in aseptic culture in response to exogenously applied ABA (: Perry & Byrne, 1969;Stewart, 1969). However, information regarding the ultrastructure of the turion is virtually non-existent.…”