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 pitcairnioid 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.

and of a weakly conduplicate-spiral type in B. gilmartinii (VARADARAJAN 1986b). The stigma of B. steyermarkii is similar to type I reported in B. reducta Baker (BROWN and GILMARTIN 1984).
Variability in types I and II is evident with regard to the (1) papillae on the lobes, (2) presence of twisted or spiraled branches, (3) duration of the spiral folding, and (4) shape and symmetry of the individual lobes.
PAPILLAE. Stigma lobes of some taxa are associated with relatively small, simple, bulbous structures known as the papillae (fig. 11). These are occasionally tubular ( fig. 8)    Our observations of the septal nectaries from representatives of Pitcairnioideae with superior, semi-inferior, and inferior ovaries confirm some structural variations reported by BUDNOWSKI (1922), e.g., the number of nectariferous channels, orifices. In taxa with superior ovaries (Deuterocohnia schreiteri, Dyckia ragonesei, and Fosterella elata), six nectariferous channels are discernible radially during the very early stages of flower development. Three channels oriented toward the septa probably constitute the primary nectariferous system. The remainder, oriented toward the placenta, may be the secondary nectariferous system (fig. 24). The latter channels are discernible only in the ovaries of pre-anthesis flowers. In some superior ovaries (Navia splendens, Cottendorfa guianensis) and semi-inferior to inferior ovaries (Pitcairnia heterophylla, Puya harmsii, fig. 27), the nectaries include only the septal channels in all developmental stages examined.
The number, orientation, persistence of the nectariferous channels, and ovary position indicate three modes of nectar release from the ovary. In superior ovaries with six radial channels or three septal channels ( fig. 27), nectar release to the exterior by the dissolution of the septal channels seems likely. The ovary surface is mostly grooved, and the septal channels break open at the grooves (figs. 23, 28). Guided by the grooves, nectar flows from the septal channels to the ovary base, where it finally accumulates.
Placental channels lose their morphological identity at anthesis as they become integrated with the placental tissue. Although the actual route of nectar flow from these channels is not well understood, it appears that their secretions are partly (1) Nectar release from the semi-inferior/inferior *' '} te; ',,' \ .' jh ovaries is slightly different from the above account. Complete epigyny results from the receptacular tissue overgrowing the ovary, beyond the level of origin of the gynoecium (ESAU 1977). Sometimes, the relative position of the inferior ovary is further complicated by the development of an epigynous tube (e.g., Ayensua). All the pitcairnioid inferior ovaries investigated have only three septal channels. Unlike the superior ovaries, the receptacular tissue peripheral to the ovary wall and sometimes the epigynous tube of an inferior ovary are conceivably the main barrier to the nectar flow to the exterior. The only remaining outlet for the nectar of these semi-inferior or inferior ovaries is, therefore, the apical orifices. Persistence of the septal channels during the post-anthesis stages of the inferior ovaries provides evidence for the above explanation.

FLORAL MORPHOLOGY AND OBSERVATIONS ON THE POLLINATION BIOLOGY
Type II stigma of Pitcairnioideae varies so widely that more than a single pollination system seems probable. The highly compact, conduplicately folded, spathulate stigma lobes ( fig. 1 1 ) with dense papillae are frequent in relatively large (often 6 cm long), tubular, scarlet to red, zygomorphic flowers of Pitcairnia with abundant nectar (P. corallina, P. meridensis, P. nubigena). These features, in combination with a fairly compact type II stigma, diurnal anthesis, tubular and/or reflexed flowers, hard flower wall, stiff filaments, and stylar base strongly indicate bird pollination (PROCTOR and YEO 1972).
Type II stigma with semicompact lobes with or without papillae ( fig. 1) also occurs in large, night blooming, white, tubular blossoms. These actinomorphic flowers occasionally produce strong odors at night and are aggregated on massive, terminal inflorescences conspicuously demarcated from the surrounding foliage (Ayensua uaipanensis, Puya aristeguietae). These features indicate bat pollination (PROCTOR and YEO 1972).
Type I or type II stigmas with ovate to lanceolate, somewhat loosely folded stigma lobes lacking papillae ( fig. S)