Callose in the walls of mature embryo sac ofTorenia fournieri

Summary During the course of a fluorescence microscopic investigation on the extra-ovular micropylar portion of the embryo sacs ofTorenia fournieri Lind. (Scrophulariaceae) a callosic wall was found which surrounded it almost completely until the time of anthesis. In addition, the walls of young synergids and the filiform apparatus also showed callosic fluorescence. Treatments with PAS reaction revealed a PAS-positive substance filling up the locular cavity. Our attempts to induce fluorochromasia by employing fluorescein diacetate failed, indicating the low permeability of the callosic wall around the embryo sac. It is assumed that the callose wall around the embryo sac isolates the latter from the contents of the locular cavity whereas the callose in the synergid walls may represent an intermediate stage in the maturation of these walls; the filiform apparatus is mainly composed of callose.