Bradleya 31/2013 pages 142-149 Coleocephalocereus purpureus has a cephalium; Micrantho - cereus streckeri has a pseudocephalium (Cereeae, Cactoideae, Cactaceae) Root Gorelick Department of Biology, School of Mathematics & Statistics, and Institute of Interdisciplinary Studies Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6 Canada. (email:
[email protected]). Photographs by the author Summary : The putatively closely related cactus Introduction genera of Coleocephalocereus , Micranthocereus , Cactaceae (cacti) in the tribe Cactoideae have Cereus , Monvillea , and Stetsonia have a wide a wide range of reproductive anatomies ranging range in specialization of reproductive portions of from cephalia to pseudocephalia to forms where the shoot, from cephalium to pseudocephalium to reproductive and vegetative structures are indis - no specialization. After briefly summarizing the tinguishable (Buxbaum, 1964, 1975; Mauseth, shifting uses of the terms ‘cephalium’ and ‘pseudo - 2006). cephalium’, I provide gross morphological evi - For instance, Melocactus Link & Otto, Disco - dence that Coleocephalocereus purpureus has a cactus Pfeiffer, and Espostoa Britton & Rose have true cephalium that is formed of a continuous true cephalia in which the flowering parts are not swath of bristles and hairs, with its underlying photosynthetic because every epidermal cell con - thick cortex of parenchyma replaced by a narrow tains a modified leaf that is a hair, bristle, or layer of cork. By contrast, Micranthocereus streck - spine, with no stomata amongst the epidermal eri has a pseudocephalium composed of nothing cells (Mauseth, 2006). Furthermore, there are more than larger hairier areoles in which the un - changes to the internal anatomy of cephalia, derlying epidermis is still photosynthetic and the where the underlying cortex is not a wide swath of underlying cortex is still a thick layer of highly succulent parenchyma, but instead a thin parenchyma without any noticeable cork.