| The present study examines the main patterns of morphological variation in all members of Pennellia Nieuwl., including P. tricornuta and P. microsperma that until recently were included in Arabis. Intensive studies of morphological and anatomical characters were conducted to resolve phylogenetic relationships within the genus and to bring about clear morphological circumscriptions of all species. The morphological work involved analysis of herbarium material, including critical examination of trichomes, flowers, fruits, seeds, and pollen by light and/or scanning-electron microscopy (SEM). Information on the 463 herbarium, as well as the 219 personal collections, was entered into two databases, one dealing with locality and the other with all aspects of morphology and anatomy.; The morphological patterns recognized herein support a new taxonomic delimitation that reduces the number of species from 11 to seven. These are Pennellia longifolia (including P. mcvaughii and P. hunnewellii), P. lasiocalycina, P. micrantha (including P. robinsonii), P. patens (including P. juncea), P. tricornuta, P. boliviensis, and P. microsperma. |
