80 AROl PEANA, Vol. 37 Elias Landolt and the Duckweeds

Walter Lämmler Landolt Duckweed Collection Spiegelgasse 12, CH-8001 Zürich, Switzerland Josef Bogner Botanischer Garten and Botanische Staatssammlung Menzinger Str. 63&67, D-80638 München, Germany

BIOGRAPHIC NOTES 1986; Landolt & Kandeler, 1987). He revised taxonomically the duckweeds for many Elias Landolt was born on July 24,1926 in floras worldwide and was also the first to Zurich, Switzerland. He read biology at suggest molecular analyses of all - the Swiss Federal Institute of Technology ceae species. Altogether he published 64 Zurich (ETH: Eidgenössische Technische papers on duckweeds, alone or with other Hochschule) where in 1950 he completed authors (see his publications list on duck- his undergraduate work on: "Synergismen weeds in References). im Bereich von Mikroorganismen", and in Scientific interests of Elias Landolt were, 1953 graduated with the Ph. D. thesis however, not limited to the duckweed "Untersuchungen über die Artengruppe family. His other passion was floristics Ranunculus montanus Willd. in den Alpen and in particular mapping distribu- unci im Jura". From 1953 to 1955 he was tions. His exceptional gift of assessing carrying out postgraduate studies at the diagnostic characteristics of was still Department of Plant Biology of the Carne- more astounding in view of his congenital gie Institution, Stanford University, Cali- color-vision deficiency: he was unable to fornia (USA), and also at the Earhard recognize red and green. He authored or Laboratory of the California Institute of co-authored a number of important floristic Technology (CALTECH) in Pasadena. This publications dealing with various regions was the beginning of his research on of Switzerland. Enclosed below is a selec- duckweeds which resulted in the First tion of his works on the subject: publication about the group (Landolt, 1955). His habilitation thesis dealt with physiological and ecological aspects of Die Artengruppen des Ranunculus monta- duckweeds, and the resulting paper was nus Willd. in den Alpen und im Jura published in 1957. From 1964 to his (Landolt, 1954) retirement in 1993 he was tenured profes- Flora der Schweiz und angrenzender sor at Swiss Federal Institute of Technology Gebiete (Hess, Landolt & Hirzel, Zurich (ETH) and from 1966 to 1993 he was 1967, 1970, 1972) also director of the Geobotanical Institute Gefährdung der Farn- und Blütenpßanzen of the same institution. He passed away in der Schweiz (Landolt, 1991) aged over 86 years on April 1, 2013. (Figs. 1 Flora der Stadt Zürich (Landolt, 2001) and 2) Unsere Alpenflora (Landolt, 2003) Flora Indicativa (Landolt et al., 2010) Only a few people in Switzerland were Flora des Sihltals (Landolt, 2013) aware that duckweeds were so important to Landolt as a subject of scientific study, and Science was obviously the main interest that he was the expert on this plant group. of Landolt, but music and art also played an Lanclolt's lifetime biosystematic studies of important role in his life. After his retire- the group based both on herbarium spec- ment in 1993 he again played the cello imens and living plants resulted in a two- regularly, in particular the suites by Bach, volume monograph of the family (Landolt, which fascinated him all over again. When \V. LAMMLER, J. BOGNI-R, 2014 .si

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Fig. 2. Landolt in the field.

Fig. 1. Professor Dr Elias Landolt. (USA) where they remained until 2009- The Biolex collection was then taken over by one day he heard about the painting Dr. Eric Lam at Rutgers University, NJ, and exhibition of Edward Hopper in Germany, renamed "Rutgers Duckweed Stock Coop- he did not mind the long travel to see the erative (RDSC)"(http.//www.ruduckweed. pictures. org (March 25, 2014)). Landolt was always modest and ready to In 2009 the maintenance of the ETH help. Colleagues and friends will well Collection at the Geobotanical Institute was remember these aspects of his personality. terminated. The ample material was then taken over personally by Elias Landolt as a The Landolt Duckweed Collection private collection under the name "Landolt Duckweed Collection". This status has For almost sixty years beginning from been maintained after the death of Landolt. 1953 Elias Landolt travelled around the W. Lämmler is presently the sole adminis- world to collect duckweeds for the so- trator of the collection which is available called "ETH Collection" at the Geobotani- for scientific purposes and open to research cal Institute of SFIT Zurich. Over this long requests. At the time being, the collection period he established in Zurich a compre- includes approximately 500 clones. The hensive and important living collection of duckweeds are cultivated sterile in test duckweeds today known as the "Landolt tubes with nutrient solution, either watery Duckweed Collection" which has been or semi-solid. The five genera of the family used as the material source for various (Spirodela Schleiden, Landoltia Les & research projects by many scientists. At its Crawford, Lemna L., Wolffiella Hegelmaier best the collection comprised over 1,000 and Woljfia Horkel ex Schleiden) are very clones. (Figs. 3 and 4) different from each other. This means that In 1997 duplicates of all strains were particular species may also differ in their given to Biolex Company in Pittsboro, NC physiological requirements and therefore 82 AROIDEANA, Vol. 37

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Fig. 3. The duckweed collection, cultivated in test tubes.

different nutrient solutions need to be family in his floristic treatments as well as used. Of the three brands of nutrient in his monograph (Landolt, 1986; Landolt solutions currently in use viz. Hutner, & Kandeler, 1987) and was adamant Hoagland, and Schenk & Hildebrandt, the about keeping on this taxonomical status. first one is made at our lab, whereas the On the other hand, Engler (1876) in one two others are available commercially. of his first publications on aroids treated It should be noted that duckweeds in the duckweeds as a subfamily of the cultivation may take on a different appear- under the name , ance from those in the wild, meaning that but later (Engler, 1889) he recognized morphological characters of certain species duckweeds as a separate family viz. the can change under optimal cultivation con- Lemnaceae. ditions. These modifications must absolute- Fossil collections, especially newer and ly be considered when cultivated specimens more complete discoveries in the last few are being determined. decades, provide evidence that today's living duckweeds belong to a lineage that existed since the Late Cretaceous. The two The Duckweeds and Their wide-spread fossil species in the Northern Phylogenetic Relationship hemisphere belong to the ancient genus Duckweeds are very small, free-floating Limnobiophyllum Krassilov, which lived on aquatic plants that most people can easily earth for about 50 million years until the recognize as a specially adapted plant Miocene (Kvacek, 1995; Slockey et al., family, the Lemnaceae. The family was first 1997), and then died out. Better known of described in 1821 (Gray, 1821). Elias Land- the two taxa is Limnobiophyllum scutatum olt maintained the Lemnaceae as a distinct (Dawson) Krassilov. \V. LÄMMLER, J. BOGNER, 2014 .S3

Fig. 5. Wolffia arrhiza (L.) Horkel ex Wimm (approx. x 30).

and the Pothoideae, which Ixjth have bisex- ual flowers. It should Ix; noted that, contrary to many authors, Landolt always considered the flowers of duckweeds as bisexual. Well, he was correct in his interpretation! The DNA results and the well preserved fossil evidence represent strong arguments in favor of including the duckweeds within the Araceae and maintaining them there as a separate subfamily, the Lemnoideae. Today, the duckweeds are highly re- duced plants which have evolved by neoteny, which means the early ontoge- netic development is fixed, and the plants Fig. 4. Test tube with Lemna perpusilla become fertile, producing reproductive Torr. organs and fruits. This is also the reason why duckweeds look so different from Limnobiophyllum was a free-floating "normal" plants, especially as far as the plant with stolons, had bigger leaves with most reduced species of the genus Wolffia first and second order venation whereas in are concerned. (Fig. 5) the less advanced Lemneae there are only With help of comparative morphological first order veins. It also had simple and studies the so-called frond of duckweeds can branched roots, its flowers were bisexual be simply explained, using the lesser re- (although they are known from only one duced Lemneae (Spin>dela, Landbltia and fossil site), and had seeds with a ribbed limita). The frond consists of a leaf where testa, thus very similar to that of the today's the distal part with the venation is homolo- duckweeds. The pollen of Limnobiophyl- gous to the leaf blade, whereas the pouches lum (in situ) is echinate and also very at the basal part of the frond represent the similar to that of the duckweeds by being petiole with a sheath which also protects monoporate with an annulus, ulcerate the new fronds and the inflorescence. The in today's duckweeds, where is also an vegetative point lies in the middle, and is very aperture (pore) where the pollen lube small resembling a liny dot. The scale below appears at germination (Bogner, 2009). the frond at the point of the root emergence New DNA studies (Cabrera el al., 2008; in Spimdela and ≤Ï≥Ë≤Ó≤≤≥‡ may be interpret- Cusunano et al., 2011; Nauheimer et al., 2012) ed as a prophyll. show that the duckweeds are nested within In older times it was believed lhat the Araceae. Their position in a phylogenetic the duckweeds are closely related to the tree lies subbasal between the Orontioideae genus Pistia L. which is by no means the 84 AROIDEANA, Vol. 37 case. There are many differences between Hess, H. E., E. Landolt & R. Flirzel. 1967. these two groups. DNA studies reveal lhat Flora der Schweiz und angrenzender Pistia is nested in the subfamily Aroideae Gebiete: Pteridophyla bis Caiyophylla- with unisexual flowers, and inaperturate ceae. Birkhäuser Verlag, Basel: pp. 858. pollen grains (Hesse, 2006). That also Hess, H. E., E. Landolt & R. Hirzel. 1970. means that the Araceae went at least twice- Flora der Schweiz und angrenzen- through a free-floating phase during their der Gebiete: Nymphaeaceae bis Pri- evolution. mulaceae. Birkhäuser Verlag, Basel: pp. 956. REFERENCES Hess, H. E., E. Landolt & R. Hirzel. 1972. Flora der Schweiz und angrenzender First listed here are the bibliographic Gebiete: Plumbaginaceae bis Compos- references used in the present article; this itae. Birkhäuser Verlag, Basel: pp. 876. part includes the few publications of other Hesse, M. 2006. Pollen wall ultrastructure authors working on duckweeds and also of Araceae and Lemnaceae in relation data on the floristic works of Landolt. to molecular classifications. Aliso. 22: Then follows the comprehensive list of his 204-208. publications on the Lemnaceae in which Kvacek, Z. 1995. Limnobiophyllum Krassi- his works on the duckweeds referred to in lov - fossil link between the Araceae the article are marked with asterisks (*). and Lemnaceae. Aquatic Botany. 50: 49-61. Bibliographic References Landolt, E. 1950. Syneigismen im Bereiche Bogner, J. 2009. The free-floating Aroids von Mikroorganismen. Diplomarbeit (Araceae) - living and fossil. Zitteli- Thesis, ETFI Institut für spezielle ana, ser. A. 48/49: 113-128. Botanik, Zürich. Cabrera, L. L., A. S. Gerardo, M. W. Chase, Landolt, E. 1954. Die Artengruppen des S.J. Mayo, J. Bogner & P. Dávila. 2008. Ranunculus montanas Willcl. in den Phylogenetic relationships of aroids Alpen und im Jura (Zytologisch-sys- and duckweeds (Araceae) inferred tematische Untersuchungen). Berichte from coding and noncoding plastic! der Schweizerischen Botanischen Ge- DNA. Am. J. Bot. 95: 1153-1165. sellschaft. 64: 9-83. Cusimano, N., J. Bogner, S. J. Mayo, P. C. Landolt, E. 1991. Gefährdung der Farn- Boyce, S. Y. Wong, M. Hesse, W. L. A. und Blutenpflanzen in der Schweiz: Hetterscheid, R. C. Keating & J. — mit gesamtschweizerischen und regio- French. 2011. Relationships within the nalen Listen. Eidgenössische Druck- Araceae: Comparison of morphologi- sachen- und Materialzentrale, EDMZ, cal patterns with molecular phytoge- Bern: pp. 185. nies. Am. J. Bot. 98: 654-668. Landolt, E. 2001. Flora der Stadt Zürich (1984- Engler, A. 1876. Vergleichende Untersu- 1998). Birkhäuser, Basel: pp. 1421. chungen über die morphologischen Landolt, E. 2003- Unsere Alpenflora. SAC- Verhältnisse der Araceae. I. Theil. Verlag, Bern: pp. 341. Natürliches System der Araceae. Nova Landolt, F.., B. Bäumler, À. Erhardt, O. Acta der Kaiserlich Leopoldiuisch- Hegg, F. Klötzli, W. Lämmler, M. Carolinisch Deutschen Akadamie der Nobis, . Rudmann-Maurer, F. H. Naturforscher. 39(3): 134-155. Schweingruber, J.-P. Theurillat, E. Engler, A. 1889. Lemnaceae, vol II. 3: Urmi, M. Vust & T. WcMgesiHJfth. 154-164 In A. Engler & K. Prantl. Die 2010. Flora indicativa - Ökologische natürlichen Pflanzenfamilien. Zeigerwerte und biologische Kennzei- Gray, J. E. 1821. A natural arrangement of chen zur fíora der Schweiz und der British plants, vol 2. London, Baldwin: Alpen. Haupt Verlag, Bern, Stuttgart, pp. 729. Wien: pp. 376. W. LÄMMLER, J. BOGNER, 2014 85

Landolt, E. 2013. Flora des Sihllals - von der Eidg. Tech. Hochschule, Stiftung Ru- Stadt Zürich his zum Höhronen. bel, in Zürich. 70(1): 142-204. Fachstelle Naturschutz Kanton Zürich: Landolt, E. 1980b. Description of six new pp. 1001 + Karten, http://www.aln. species of Lemnaceae. Veröffentlichun- zh.ch/intemet/baudirektion/aln/de/ gen des Geobotanischen Institutes der naturschutz/veroeffentlichungen.html Eidg. Tech. Hochschule, Stiftung Rubel, (March 25, 2014). in Zürich. 70: 22-29. Nauheimer, L., D. Metzler & S. S. Renner. Landolt, E. 1980c. Key to the determination 2012. Global history of the ancient of taxa within the family of Lemna- monocot family Araceae inferred with ceae - Biosystematic investigations in models accounting for past continen- the family of duckweeds (Lemna- tal positions and previous ranges ceae), vol 1. Veröffentlichungen des based on fossils. New Phytology. 195: Geobotanischen Institutes der Eidg. 938-950. Tech. Hochschule, Stiftung Rubel, in Stockey, R. A., G. L. Hoffman & G. G. W. Zürich. 70(1): 13-21. Rothwell. 1997. The fossil monocot Landolt, E. & . Urbanska-Worytkiewicz. Limnobiophyllum scutatum: Resolv- 1980. List of the studied Lemnaceae ing the phylogeny of Lemnaceae. samples: origin and chromosome Am. J. Bot. 84: 355-368. numbers. Veröffentlichungen des Geo- botanischen Institutes der Eidg. Tech. Publications on the Lemnaceae Hochschule, Stiftung Rubel, in Zürich. 70(1): 205-247. •Landolt, E. 1955. Über das Wachstum in Landolt, E. 1981. Distribution pattern of the der Dunkelheit bei einigen Lemnac- family Lemnaceae in North Carolina. een. Verhandlungen der Schweizer- Veröffentlichungen des Geobotanischen ischen Naturforschenden Gesellschaft. Institutes der Eidg. Tech. Hochschule, 135: 135-136. Stiftung Rubel, in Zürich. 77: 112-148. *Landolt, E. 1957. Physiologische und Landolt, E. 1982a. Distribution pattern and ökologische Untersuchungen an Lem- ecophysical characteristics of the Eu- naceen. Berichte der Schweizerischen ropean species of the Lemnaceae. Botanischen Gesellschaft. 67: 271- Berichte des Geobotanischen Institutes 410. der Eidg. Techn. Hochschule, Stiftung Landolt, E. 1975. Morphological differenti- Rubel. 49: 127-145. ation and geographical distribution of Landolt, E. 1982b. Distribution patterns the Lemna gibba - within the family Lemnaceae, 313 In group. Aquatic Botany. 1(4): 345-363. J. J. Symoens, S. S. Hooper & P. Landolt, E. & O. Wildi. 1977. Ökologische Compère (eds.), Studies on Aquatic Felduntersuchungen bei Wasserlinsen Vascular Plants. Royal Botanical So- (Lemnaceae) in den südwestlichen ciety of Belgium, Brussels. Staaten der USA. Berichte des Geobo- Landolt, E. & W. Dann. 1983. Vergleich von tanischen Institutes der Eidg. Techn. zehn Klonen von Lemna gibba bei Hochschule, Stiftung Rubel. 44: 104- verschiedenen Stickstoffkonzentratio- 146. nen. Berichte des Geobotanischen In- Landolt, E. 1979. Lemna minúscula Herter stitutes der Eidg. Techn. Hochschule, (= L. minima Phil.), eine in Europa Stiftung Rubel. 50: 86-96. neu eingebürgerte amerikanische Landolt, E. 1984a. Flowers and fruits in the Wasserpflanze. Berichte des Geobota- genus Wolffiella (Lemnaceae). Ber- nischen Institutes der Eidg. Techn. ichte des Geobotanischen Institutes Hochschule, Stiftung Rubel. 46: 86-89. der Eidg. Techn. Hochschule, Stiftung Landolt, E. 1980a. Bibliographie der Fa- Rubel. 51: 164-172. milie der Lemnaceae. Veröffentlichun- Landolt, E. 1984b. Verbreitungsmuster in gen des Geobotanischen Institutes der der Familie der Lemnaceae und ihre Sí, AROIDEANA, Vol. 37

ökologische Deutung. Verhandlungen Landolt, E. 1992b. Lemna teñera Kurz, a der Gesellschaft für Ökologie. 12: 241- little known species of Lemnaceae. 253. Berichte des Geobotanischen Institutes Uotila, P., A. Baytop & E. Landolt. 1984. der Eidg. Techn. Hochschule, Stiftung Duckweeds (Lemnaceae) in Turkey. Rubel. 58: 124-131. Webbia. 38: 839-844. Landolt, E. 1992c. Lemnaceae duckweed •Landolt, E. 1986. The family of Lemnaceae family. J. Arizona-Nevada Acad. Sci- - a monographic study, vol 1 - ence. 26(1): 10-14. Biosystematic investigations in the Landolt, E. 1992d. Wolffieila cándala, a new family of duckweeds (Lemnaceae), Lemnaceae species from the Bolivian vol 2. Veröffentlichungen des Geobo- Amazon region. Berichte des Geobota- tanischen Institutes der Eidg. Tech. nischen Institutes der Eidg. Techn. Hochschule, Stiftung Rubel, in Zürich. Hochschule, Stiftung Rubel. 58: 121- 71(1): 566. 123. Landolt, E. 1987a. Eco-geographical Differ- Crawford, D. J. cS: E. Landolt. 1993. entiation in Some Aquatic Plants: the Allozyme Studies in Spirodela (Lem- Lemnaceae, pp. 201-215 In K. M. naceae): Variation among Conspecific Urbanska (ed.), Differentiation Pat- Clones and Divergence among the terns in Higher Plants. Academic Species. Syst. Bot. 18(3): 389-394. Press, London. Landolt, E. 1993- Species names in current use in the Lemnaceae (Monocotyle- •Landolt, E. & R. Kandeler. 1987. The dones), pp. 147-150 In W. Greuter family of Lemnaceae - a monographic (ed.), NCU-2: Names in Current Use in .study, vol 2 - Biosystematic investiga- the Families Trichocomaceae, Clado- tions in the family of duckweeds niaceae, Pinaceae and Lemnaceae. (Lemnaceae), vol 4. Veröffentlichun- Koeltz Scientific Books, Königstein, gen des Geobotanischen Institutes der Deutschland. Eidg. Tech. Hochschule, Stiftung Ru- Crawford, D.J. & E. Landolt. 1994. Allozyme bel, in Zürich. 95(2): 1-638. diversity within and divergence among Landolt, E. 1988. Wasserlinsen, die klein- species of Wolffia (Lemnaceae). Am. J. sten Blütenpflanzen der Erde. Mittei- Bot. 81(6, suppl.): 150. lungen der Naturforschenden Gesell- Landolt, E. 1994a. The Lemnaceae of schaft in Bern. 45: 188-189- Zimbabwe and Botswana. Berichte Landolt, E. & A. Lawalrée. 1988. Lemna- des Geobotanischen Institutes der Eidg. ceae, pp. 1-12 In P. Bamps (ed.), Techn. Hochschule, Stiftung Rubel. 60: Flore d'Afrique centrale (Zaire - 110-136. Rwanda - Burundi) Spermatophytes. Landolt, E. 1994b. and Ecology Jardin botanique national de Belgi- of the Section Wolffia of the Genus que, Meise. Wolffia (Lemnaceae). Berichte des Landolt, E. 1989. Geographisch-ökolo- Geobotanischen Institutes der Eidg. gisches Vorkommen der Lemnaceae- Techn. Hochschule, Stiftung Rubel. Arten in der Schweiz im Rahmen ihrer 60: 137-151. Gesamtverbreitung. Flora. 182(1-2): Landolt, E. & . Zarzycki. 1994. Ecological 87-98. field investigations of duckweed Landolt, E. 1990. Über zwei seit kurzer Zeit (Lemnaceae) in Argentina. Berichte in Europa neu beobachtete Lemna- des Geobotanischen Institutes der Arten. Razprave. 31(8): 127-135. Eidg. Techn. Hochschule, Stiftung Landolt. E. 1992a. The flowers of Wolffia Rubel. 60: 62-109. australiana (Lemnaceae). Berichte Les, D. H., E. Landolt & D. J. Crawford. des Geobotanischen Institutes der 1994. Molecular systematica of the Eidg. Techn. Hochschule, Stiftung Lemnaceae. Am. J. Bot. 81(6, suppl.): Rubel. 58: 132-137. 168-169. W. LAMMLER, J. BOGNER, 201 I 87

Wolff, P. & E. Landolt. 1994. Spread of Handbuch der Planzenanatomie - Lemna turionifera (Lemnaceae), the Extreme Adaptations in Angiosperms red duckweed, in Poland. Fragm. Hydrophytes. Gebrüder Borntraeger, Flor. Geobol. 39(2): 439-451. Berlin. Crawford, D. J. & E. Landolt. 1995. Landolt, E. 1998b. Lemnayungensis, a new Allozyme divergence among species duckweed species from rocks of the of Wolffia (Lemnaceae). Plant Syst. Andean Yungas in Bolivia. Bull. Geo- Evol. 197(1-4): 59-69. bol. Inst. ETH. 64: 15-21. Crawford, D. J., E. Landolt, D. Les & E. Landolt, E. 1998c. Lemna, Spirodela, Wolffia, Tepe. 1995. Allozyme divergence pp. 287-288, 489, 549 In R. Wisskirchen among species of Wolffiella (Lemna- & H. Haeupler (eds.), Standardliste der ceae). Am. J. Bot. 82(6, suppl.): 122- Farn- und Blütenpflanzen Deutsch- 123. lands. Ulmer, Stuttgart. Crawford, D. J., E. Landolt & D. H. Les. Landolt, E. 1998d. Lemnaceae, pp. 264-270 1996. An allozyme study of two sibling In K. Kubitzki (ed.), The Families and species of Lemna (Lemnaceae) with Genera of Vascular Plants. Springer, comments on their morphology, ecol- Berlin. ogy and distribution. Bull. Torrey Bot. Landolt, E. 1999. Pleustonic communities Club. 123(1): 1-6. with Lemnaceae in South America. Landolt, E. 1996a. Duckweeds (Lemna- Appl. Vegetation Sei. 2(1): 7-16. ceae): Morphological and Ecological Landolt, E. 2000. Contribution on the Characteristics and their Potential for Lemnaceae of Ecuador. Fragm. Flor. Recycling of Nutrients. Environ. Res. Geobot. 45(1-2): 221-237. Forum. 5-6: 289-296. Landolt, E. 2000. Lemnaceae Gray, 22: Landolt, E. 1996b. Lemnaceae S. F. Gray, 143-153 In Flora of North America. 21: 1-8 In Flora Fanemgdmica Argen- Crawford, D. J., E. Landolt, D. H. Les & tina. Córdoba. R. T. Kimball. 2001. Allozyme studies Crawford, D. J., E. Landolt, D. H. Les & E. in Lemnaceae: variation and relation- Tepe. 1997. Allozyme variation and ships in Lemna sections Alatae and the taxonomy of Wolffiella. Äqual. Biformes. Taxon. 50(4): 987-999. Bot. 58(1): 43-54. Landolt, E. 2001. Lemnaceae, pp. 394-399 Landolt, E. 1997a. How do Lemnaceae In T. Santisuk & K. Larsen (eds.), Flora (duckweed family) survive dry condi- of Thailand. Bangkok. tions Bull. Geobol. Inst. ETH. 63: Les, D. H., D. J. Crawford, E. Landolt, J. D. 25-31. Gabel & R. T. Kimball. 2002. Phylogeny Landolt, E. 1997b. Lemnaceae, pp. 51-54 and Systematics of Lemnaceae, the In S. Edwards, M. Tadesse & I. Duckweed Family. Syst. Bot. 27(2): 221- Hedberg (eds.), Flora of Ethiopia 240. and Eritrea. Empela, Addis Abeba. Kimball, R. T., D. J. Crawford, D. H. Les & Les, D. H., D. J. Crawford, E. Landolt, R. E. Landolt. 2003. Out of Africa: mo- Aakjar & E. Tepe. 1997a. Systematica lecular phylogenetics and biogeogra- of Lemnaceae revisited. Am. J. Bot. phy of Wolffiella (Lemnaceae). Biol. J. 84(6, suppl.): 211. Linn. Soc. 79(4): 565-576. Les, D. H., E. Landolt ¿i D. J. Crawford. Les, D. H., D. J. Crawford, R. T. Kimball, M. 1997b. Systematica of the Lemnaceae L. Moody & E. Landolt. 2003. Bioge- (duckweeds): inferences from micro- ography of discontinuously distribut- molecular and morphological data. ed hydrophytes: a molecular appraisal Plant Syst. Evol. 204(3-4): 161-177. of intercontinental disjunctions. In- Landolt, E. 1998a. Anatomy of the Lemna- tern./ Plant Sei. 164(6): 917-932. ceae (duckweeds), pp. 1-127 In S. Crawford, D. J., E. Landolt, D. H. Les, J. K. Carlquist, D. F. Cutler, P. Fink, P. Archibald & R. T. Kimball. 2005. Allo- Ozenda, I. Roth & H. Ziegler (eds.), zyme variation within and divergence 88 AROIDEANA, Vol. 37

between Lemna gibba and L disperma: ü, H. & E. Landolt. 2010. Lemnaceae, 23: Systematic and biogeographic implica- 80-83 In Z. Wu, P. H. Raven & D. Hong tions. Aquat. Bot. 83(2): 119-128. (eds.), Flora of China. Science Press, Crawford, D. J., E. Landolt, D. H. Les & R. Missouri Botanical Garden, Beijing, St. T. Kimball. 2006. Speciation in duck- Louis. weeds (Lemnaceae): phylogenetic and Landolt, E. 2011. Lemnaceae, pp. 274-282 ecological inferences. Aliso. 22: 231- In A. Wilson (ed.), Flora of Australia - 242. to Árales. ABRS and Landolt, E. & U. Schmidt-Mumm. 2009- CSIRO Publishing, Canberra and Mel- Lemnaceae, pp. 1-54 In J. Betancur, bourne, Australia. G. Galeano & C. J. Aguirre (eds.), Bog, M., P. Schneider, F. Hellwig, S. Flora de Colombia. Universidad Na- Sachse, E. Z. Kochieva, E. Martyro- cional de Colombia, Bogotá. sian, E. Landolt & K.-J. Appenroth. Bog, M., H. Baumbach, U. Schween, F. 2013- Genetic characterization and Hellwig, E. Landolt & K.-J. Appenroth. barcoding of taxa in the genus Wolffia 2010. Genetic structure of the genus Horkel ex Schleid. (Lemnaceae) as Lemna L. (Lemnaceae) as revealed by revealed by two plastidic markers and amplified fragment length polymor- amplified fragment length polymor- phism. Planta. 232: 609-619. phism (AFLP). Planta. 237(1): 1-13-