Najadaceae

  • R. R. Haynes
  • L. B. Holm-Nielsen
  • D. H. Les
Chapter
Part of the The Families and Genera of Vascular Plants book series (FAMILIES GENERA, volume 4)

Abstract

Monoecious or rarely dioecious, annual or rarely perennial, erect, caulescent, glabrous herbs of fresh or brackish waters, growing entirely submersed. Roots fibrous, few, nonseptate, at base of stem and lower nodes. Stems slender, much branched, sometimes armed with spinulose teeth on the internodes; turions and tubers never developed. Leaves spiral, subopposite or pseudoverticillate, sessile, with sheathing base; blade linear, flattened, 1-veined, sometimes abaxially toothed on midrib, the margins serrulate to dentate, the apex acute to acuminate, with 1–3 teeth per side; the teeth multicellular, formed by layers of cells decreasing in cell number distally and terminated by a large, sharp-tipped cell, or unicellular; sheaths variously shaped, each enclosing a pair of tiny intravaginal squamules, the margins usually spiny-toothed, with 1–15 teeth per side. Flowers axillary, solitary, or clustered, imperfect, perianth absent. Staminate flowers mostly subtended by 1 or 2 clear to pale purple, membranous, spathe-like envelopes, each flower consisting of a single stamen; pedicels at first short, elongating at anthesis, pushing the anther through the outer envelope; anther sessile, 1- or 4-sporangiate, dehiscing by an apical slit. Carpellate flowers sessile; a clear to pale purple membranous envelope rarely present; gynoecium ending in a short style with 3 or 4 branches; ovary 1-loculed; wall delicate, 2 cell layers thick; placentation basal; ovule solitary, bitegmic, anatropous. Fruit achenelike; gynoecial wall closely enveloping the seed, opening by decay. Seed fusi-form to elliptic; testa areolate; embryo elongate, macropodous, straight or rarely curved; endosperm developing nuclear, absent in the mature seed.

Keywords

Starch Chlorophyll Germinate Cretaceous Flavonoid 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • R. R. Haynes
  • L. B. Holm-Nielsen
  • D. H. Les

There are no affiliations available

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