XVI International Botanical Congess

The trichomes of Hedera have been documented for their usefulness in delimiting taxa, but have not been critically examined for all species. Scanning electron microscopy and light microscopy were used to examine the surfaces of leaves and fruit of 18 taxa of Hedera. Three main trichome types were identified: i) Stellate with 3-10 rays found west and north of the Mediterranean, ii) Large scale-like with 7-20 rays and average diameter of 0.24-0.3mm, found in northern Africa and west of the Mediterranean, and iii) Small scale-like with 9-25 rays and average diameter of 0.15 to 0.19mm, found east of the Mediterranean. Species with stellate trichomes on juvenile leaves have smaller, more scale-like trichomes on mature plants, while some species with scale-like trichomes on juvenile leaves have more stellate trichomes with fewer rays on mature plants. Unique cuticular patterns also exist.