The floral development and floral anatomy ofChrysosplenium alternifolium, an unusal member of the Saxifragaceae

Abstract

The floral development and anatomy of Chrysosplenium alternifolium were studied with the scanning electron microscope and light microscope to understand the initiation sequence of the floral organs and the morphology of the flower, and to find suitable floral characters to interpret the systematic position of the genus within the Saxifragaceae. The tetramerous flower shows a highly variable initiation sequence. The median sepals and first stamens arise in a paired sequence resembling a dimerous arrangement, but the first sepal and stamen arise on the side opposite to the bract. Transversal sepals and stamens emerge sequentially, as one side often precedes the other;, sepals and stamens occasionally arise on common primordia. Initiation of the gynoecium is more constant with two median carpel primordia arising on a sunken floral apex. Several flowers were found to be pentamerous with a 2/5 initiation sequence. Rowers were invariably found to be apetalous without traces of petals in primordial stages; this condition is interpreted as an apomorphy. It is postulated that the development of a broad gynoecial nectary is responsible for the occurrence of an obdiplostemonous androecium. The gynoecium shows a number of anatomical particularities not observed in other Sexifragaceae. The presence and distribution of colleters is discussed.

Foliar colleters inMacrocarpaea obtusifolia(Gentianaceae): anatomy, ontogeny, and secretion

“…Renobales et al (2001) also considered the colleters of Gentianaceae as trichomes, although no ontogenetic studies were conducted. However, Decraene et al (1998) emphasized that colleters differ from ordinary multicellular trichomes in having a specific position and function, e.g., as protecting the developing meristem by producing a viscous secretion.…”