XVI International Botanical Congess

Seven species and one variety of Hypericum are registred in Mexico: anagalloides, formosum, galinum, mutilum, pauciflorum, philonotis, silenoides and silenoides var.mexicanum, which correspond to sections Euhypericum, Brathys and Trigynobrathys. A wide morphological variation exists among them. Two groups are found in foliar antomy,in one,leaves are with thick cuticle and collenchyma,vascular bundles with more 50 conductive elements and paracytic and hemiparacytic stoma,in the other the cuticle and collenchyma are thin,vascular bundles with 15-20 elements and stoma anomocytic and anisocytic.These characteristics seems to be due to the adaptation to environmental conditions,however in the Central part of Mexico,there are populations with intermediate anatomic characteristics which indicates the possible hybrid formation in this area,such as, H.galinum x H.pauciflorum, H.silenoides x H.philonotis, and an species evolution centre.