Wood, bark and stem anatomy of New World species of Gnetum

Abstract

Quantitative and qualitative data are presentrd for I 1 collections of six species. The wide range or character states for the species is presented in thr form oTa key to emphasize their potential systematic correlations. Distinctive among these are pliellrni characteristics. Fibre-tracheids are newly reported for lianoid Gnetum species. Cells previously thought to be like companion cells in secondary phloem are shown to be uniseriate rays, counterparts to uniseriate xylem rays. Laticifers are abundant in most of thr species, and are newly described for secondary tissues of Gneturn. Presence of tyloses in laticifers of two species is apparently a new report for vascular plants. Tori are prcsent in two New World Gneturn species, adding to the report in African species. Perforation plates arc simple except near or in primary xylem, where they are simple or foraminate. Torus presence and foraminate perforation plate presence are features more reminiscent of Ephedra and other gymnosperms than of angiosperms. 'l'hc bark of Gnetuni is also very similar to that or Ephedra. 01996 The Litincan Societv of London ADDITIONAL