MORPHOLOGY,FINE STRUCTURE,AND ONTOGENY OF THE STINGING EMERGENCE OF URTICA DIOICA

Stinging emergences in Urtica dioica L. characteristically possess an elongate stinging cell and a multicellular pedestal. The emergence is derived from the epidermal and subepidermal cell layers. The apical wall of the stinging cell is composed of silica bodies which decrease basipetally in concentration. The basal portion of the cell wall of the stinging cell is devoid of silica bodies and lacks primary pit fields or pits between it and the pedestal cells. X-ray microanalysis of electron dense particles located in the stinging cell ER-golgi complex indicate that these particles contain silicon. There is no ultrastructural evidence for the presence of a toxin synthesizing system or a toxin itself.