The development of the staminal filament of Gasteria verrucosa

The development of the lower part of the stamen of Gasteria verrucosa (Mill.) H. Duval, the filament, was investigated using interference contrast, transmission and scanning electron microscopy, and was related to the development of the anther. The filament extends during its entire development, in the younger stages mainly in the basal region, in the older stages in the tip. Up to maturity the solidity is gradually improved by the progressive thickening of the tangential epidermal wall and the cuticle from the tip to the base of the filament and the increasing turgidity of the epidermis. The amount of tracheary elements increases up to maturity as does the starch content of the epidermis and the parenchyma. Starting at the pollen mitosis stage, a progressive cytoplasmic degeneration can be observed from the tip to the base and from the central parenchyma to the epidermis. At anther dehiscence the filament tip shrivels and the starch has disappeared from the entire filament. Both the latter phenomenon and the cytoplasmic degeneration may be due to redistribution of substances to other floral parts. The presence of prominent intercellular spaces may be important for the supply of gas to the maturating locule.