Indumentum types of the leaves in 31 species of Potentilla L.(Rosaceae) and four related genera, especially Tylosperma Botsch., Schistophyllidium (Juz.ex Fed.) Ikonn.
, Drymocallis Fourr.ex Rydb., and Sibbaldia L.from Iran were investigated.Indumentum ultrastructure was studied by scanning electron microscopy (SEM).
SEM observation revealed three type classes based on leaf indumentum: 1) straight (appressed-erect); 2) straight-erect and crispate, and 3) crispate-floccose.The Pedal Exercisers straight hair character (I type class) is widely distributed among all genera sampled and six sections of Potentilla.In contrast the crispate-floccose indumentum (III type class) is confined to all examined species of sections Speciosae and Pensylvanicae.While some sections especially Rectae (straight and straight-crispate hairs) and Terminales (straight-crispate and floccose-crispate) posses two indumentum type classes.The present survey shows that indumentum types are of systematic importance and may form good Outerwear key characters for identification purposes.