Morphological Variation of Some Floral Features of the Subfamily Pitcairnioideae (Bromeliaceae) and Their Significance in Pollination Biology

Scanning electron and light microscopy observations of wet-preserved flowers of Bromeliaceae subfamily Pitcaimioideae yield new information on the stigma, petal scales, and septal nectaries. Variations of the stigma types are evident among several genera. The gross structural features of the stigma do not indicate definite pollination trends, but the shape of the lobes and papillae indicate a few specific modes. In pit­caimioid genera, petal scales, when functional, may aid in pollination by accumulating the nectar secreted from the ovary, thus facilitating its availability to the pollinator. Nectaries associated with the gynoecia usually display tripartite channels in the ovary septa. Some developmental changes of the channel structure and position of the ovary indicate three probable modes of nectar release from the gynoecia of the pitcair­nioids: (1) through lateral grooves or openings, (2) partly through the apical orifices and partly through the dissolved areas of the spetal channels, and (3) exclusively through the apical orifices. Analysis of a wide range of floral features indicates that ornithophily, chiropterophily, and entomophily exist in different Pit­cairnioideae lineages.