| Abstract: | The ultrastructure and histochemistry of the refractile, vesiculate cells (“blasenzellen,”“cellules secretrices,”“gland cells”) of Antithamnion defectum Kylin were examined. The refringent vacuolar contents disclosed two components of differing density: an electron opaque, proteinaceous matrix material surrounding cores of irregularly shaped, less opaque material. The cores contain less protein and more unknown material than the matrix. Part or all of the vacuolar material is synthesized by abundant rough endoplasmic reticulum (ER) and deposited in smooth surfaced cisternae that swell to form vesicles. Mitochondria are usually associated with stacks of the swelling cisternae. The vesicles enlarge by continued deposition of synthesized material and coalescence with other vesicles. All vesicles eventually coalesce to form the mature vacuole. A crystalline array of fibrils develops in the cytoplasm during later stages of vacuole enlargement. The crystal contains a sulfated, acidic polysaccharidic material. The chloroplasts, if present, and nucleus degenerate at vacuole maturity. Active release of the vacuolar material does not occur, and organelles for extracellular secretion are not present. Structural evidence suggests a storage, rather than secretory, function for the cells. |
