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Azollaceae

  • J. J. Schneller
Chapter
Part of the The Families and Genera of Vascular Plants book series (FAMILIES GENERA, volume 1)

Abstract

Free floating aquatic plants with copiously branched, delicate, horizontal, protostelic stems. Roots simple, on the ventral side of the axis, chlorophyllous, solitary or in clusters, extending a short distance downward in the water, deciduous. Leaves sessile, alternate, in two rows in the dorsal side of the stem; each leaf divided into two lobes, a (usually somewhat smaller) upper, aerial, and a lower floating lobe. The upper, aerial lobe photosynthetic, with epidermis and mesophyll, bearing on the lower surface a large cavity with mucilage and usually living colonies of the blue-green alga Anabaena; the lower lobe floating with the dorsal side only immersed, unistratose except at the base, mostly without chlorophyll. Sporocarps borne on the first leaf of a lateral branch, the lower lobe of this fertile leaf reduced to two, sometimes up to four sporocarps, the upper lobe forming an involucre covering the sporocarps. Sporocarps containing either micro- or mega-sporangia; megasporocarps smaller. Sporangia without dehiscence mechanism. Microsporocarps containing numerous microsporangia; microsporangia forming 64 [according to Svenson (1944) 32 or 64] trilete spores; clusters of spores embedded in 3–10 massulae (massula: hardened tapetal mucilage containing groups of spores); surface of the massulae mostly with anchor-shaped outgrowths, called glochidia, except in A. nilotica. Megasporocarp containing only one mega-sporangium; Megasporangium with 8 spore-mother cells; after meiosis only one spore developing, the others aborting. Mature megaspore on the proximal pole with a columella, hair-like filaments, and with apical massulae (called floats). Megaspores plain, perforate, with sparse excrescences, or granulate, with dense excrescences, or densely filamentose, with fine or coarse perforations, or compact filaments forming a reticulum over coarse perforations, or rugulate, with mostly obscure perforations; microspores rugulose, germinating within the massula; microprothallium reduced, with one antheridium. Megaprothallium developing within megaspore, the growing cell cushion then forcing the megaspore open at the laesura, forming a (in transversal section) round to triradiate prothallium with several archegonia on the upper surface. C. 6 species, in the New World from Argentina to Alaska, in the Old World in Africa, E. Asia and Australia; introduced into Europe.

Keywords

Lower Lobe Proximal Pole Reticulate Evolution Fertile Leaf Compact Filament 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Bibliography

  1. Bonnet, A. L. M. 1957. Contribution à l’étude des Hydroptéridées. III. Recherches sur Azolla filiculoides Lamk. Rev. Cytol. Biol. Vég. 18: 1–88.Google Scholar
  2. Campbell, D. H. 1893. On the development of Azolla filiculoides Lam. Ann. Bot. ( London ) 7: 155–187.CrossRefGoogle Scholar
  3. Demalsy, P. 1958. Nouvelles recherches sur le sporophyte d’ Azolla. Cellule 59: 235–268.Google Scholar
  4. Duckett, J. G., Toth, R., Soni, S. L. 1975. An ultrastructural study of the Azolla-Anabaena azollae relationship. New Phytol. 75: 111–118.CrossRefGoogle Scholar
  5. Duncan, R. F. 1940. The cytology of sporangium development in Azolla filiculoides. Bull. Torrey Bot. Club 67: 391–412.CrossRefGoogle Scholar
  6. Eames, A. J 1936. Morphology of vascular plants, lower groups. London: McGraw-Hill.Google Scholar
  7. Follieri, M. 1977. Classification and phylogeny of living and fossil water ferns of the genus “Azolla”. Webbia 31: 97–104.CrossRefGoogle Scholar
  8. Fowler, K. 1975. An escape mechanism for spermatozoids in Azolla massulae. Amer. Fern J. 65: 7–10.CrossRefGoogle Scholar
  9. Fowler, K., Stennet-Willson, J. 1978. Sporoderm architecture in modern Azolla. Fern Gaz. 11: 405–412.Google Scholar
  10. Hall, J. W. 1969. Studies on fossil Azolla: primitive types of megaspores and massulae from the Cretaceous. Amer. J. Bot. 56: 1173–1180.CrossRefGoogle Scholar
  11. Holst, R. W., Yopp, J. H. 1979. Studies of the Azolla-Anabaena symbiosis using Azolla mexicana. I. Growth in nature and laboratory. Amer. Fern J. 69: 17–25.CrossRefGoogle Scholar
  12. Konar, R. N., Kapoor, R. K. 1972. Anatomical studies on Azolla pinnata. Phytomorphology 22: 211–223.Google Scholar
  13. Konar, R. N., Kapoor, R. K. 1974. Embryology of Azolla pinnata. Phytomorphology 24: 228–261.Google Scholar
  14. Loyal, D. S. 1958. Cytology of two species of Salviniaceae. Curr. Sci. 27: 357–358.Google Scholar
  15. Loyal, D. S., Gollen, A. K., Ratra, R. 1982. Morphological and cytotaxonomic observations on Azolla pinnata. Fern Gaz. 12: 230–232.Google Scholar
  16. Lucas, R. C., Duckett, J. G. 1980. A cytological study of the male and female sporocarps of the heterosporous fern Azolla filiculoides Lam. New Phytol. 85: 409–418.CrossRefGoogle Scholar
  17. Peters, G. A., Toia, R. F., Raveed, D., Levine, N.J. 1978. The Azolla - Anabaena relationship. VI. Morphological aspects of the association. New Phytol. 80: 583–593.CrossRefGoogle Scholar
  18. Pieterse, A. H., de Lange, L., van Vliet, J. P. 1977. A comparative study of Azolla in the Netherlands. Acta Bot. Neerl. 26: 433–449.Google Scholar
  19. Rao, H. S. 1935. The structure and life history of Azolla pinnata R. Brown with remarks on the fossil history of the Hydropterideae. Proc. Indian Acad. Sci. 2B: 175–200.Google Scholar
  20. Reed, C. F. 1954. Index Marsileata et Salviniata. Bol. Soc. Brot. II, 28: 5–61.Google Scholar
  21. Reed, C. F. 1965. Index Marsileata et Salviniata. Suppl. Bol. Soc. Brot. II, 39: 259–302.Google Scholar
  22. Strasburger, E. 1873. Über Azolla. Jena: Gustav Fischer.Google Scholar
  23. Svenson, H. K. 1944. The New World species of Azolla. Amer. Fern J. 34: 69–84.CrossRefGoogle Scholar
  24. Sweet, A. R., Hills, L. V. 1976. Early tertiary species of Azolla subg. Azolla sect. Krematospora from western and arctic Canada. Can. J. Bot. 54: 334–351.CrossRefGoogle Scholar
  25. Takhtajan, A. L. 1953. Phylogenetic principles of the system of higher plants. Bot. Rev. 19: 1–45.CrossRefGoogle Scholar
  26. Tschermak-Woess, E., Dolezal-Janisch, R. 1959. Über die karyologische Anatomie einiger Pteridophyten sowie auffallende Unterschiede im Kernvolumen bei Cyrtomium falcatum. Österr. Bot. Z. 106: 315–324.CrossRefGoogle Scholar
  27. Warmbrodt, R. D., Evert, R. F. 1978. Comparative leaf structure of six species of heterosporous ferns. Bot. Gaz. 139: 393–429.CrossRefGoogle Scholar

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© Springer-Verlag Berlin Heidelberg 1990

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  • J. J. Schneller

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