In the three subfamilies of Bromeliaceae identification to genus is progressively more difficult. Most members of the Pitcairnioideae can be so identified even when in fruit, while those of the Tillandsioideae require good flowers in many if not most cases. The Bromelioideae, treated in this volume, are a step worse in that their genera are so poorly defined that even with complete information it is difficult to assign some species to genera. They have all the characters used to define genera in the other subfamilies and pollen districtions as well, yet they produce bigeneric hybrids with ease. It would seem that they have developed so much more recently than the genera of Pitcairnioideae and Tillandsioideae that they have not set up the fertility barriers obtaining in the older subfamilies. The treatment of Bromeliaceae subfamily Bromelioideae in this volume includes artificial keys, descriptions, distribution maps, and black and white illustrations for efficiency in identification.