Abstract:
Environmental conditions encountered in arid ecosystems differ vastly from those in more mesic ecosystems. Dispersal
strategies in arid environments refl ect these differences and many mechanisms have evolved that restrict or hinder dispersal.
Myxospermy is a trait developed by plant species from arid regions to restrict diaspore dispersal by means of an anchorage
mechanism. Several of the abundant plant species in Namaqualand, within the arid Succulent Karoo Biome, display myxospermy.
Diaspores of these species produce copious amounts of mucilage when they are moistened and are anchored to the
soil once the mucilage dries out again. This study investigated the origin of the mucilaginous layer of 12 species anatomically,
using both light and scanning electron microscopy. The mucilage production of the species investigated could best be grouped
into three types: 1, epidermal and sub-epidermal cells of seeds and achenes; 2, specialized tissue in wings or the pappus of
achenes; and 3, mucilage excreting hairs. Previous systems for classifying the different types of mucilage production did not
recognize the mucilaginous nature of wings or a pappus. A short note on the composition of the mucilage is included.
