gnetophyta

There exist three genera of gnetophytes. Each is unique in many ways...

EPHEDRA

  • Approximately 35 species
  • The only genus of gnetophyta found in the United States
  • Most species inhabit arid or desert regions
  • Shrubs are profously branched with small, scale-like leaves and jointed stems

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    WELWITSCHIA
    "The most bizarre of vascular plants"

  • One species
  • Found only in the Namib and Mossedemes deserts in southwestern Africa
  • Live on rocky benches or in dry stream beds
  • The majority of the plant is burried in sand
  • The exposed part consists of a massive, woody disc from which its strap-shaped leaves protrude
  • Survives mostly on fog and dew
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    GNETUM

  • Approximately 30 species
  • Thrive in the moist tropics
  • Consist of trees and climbing vines with large, leathery leaves
  • The alkaloid phedrine obtained from one species is used in hospitals to contract blood vessels and to alleviate asthma

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    The genera also share many characteristics

    Gnetophytes have many angiosperm-like features. They are sometimes considered to be the link between angiosperms and gymnosperms. Gnetophytes are currently considered to be specialized endpoints of one line of gymnosperm evolution.

  • They contain primitive types of vessels in the secondary xylum
  • They have both compound androstrobilly and gynostrobilly
  • The leaves are commonly opposite or whorled
  • There are no resin canals

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