The presence of small knobs/nodules found on the adaxial leaflet surface of some
Encephalartos species was investigated in 134 cycad species of nine genera. The knobs,
referred to as collicles, were found to be the result of connecting mucilage canal ‘bridges’
over vascular bundles, connecting mucilage canals situated between adjacent parallel
vascular bundles. Collicles were found on some Encephalartos species only and not
always on all individuals of the same species. The possible taxonomic value of these
collicles is discussed.