The gametophyte of acrostichum aureum L.

Abstract

The spores of A. aureum are trilete and granulose. On germination, a 6-10 cells long germ filament is produced, in which growth is mainly by intercalary formation of new cells rather than by cell elongation. One or two of the terminal cells become quiescent soon, and the intercalary cells form a prothallial plate. Cells on one side of the plate are more active than those on the other, and a broad ameristic lateral lobe is developed by their activity. As the lobe becomes spatulate, a multicellular meristem is differentiated from marginal cells on the side facing the posterior end of the germ filament. By the activity of the meristem the prothallus becomes cordate, with the meristem at the bottom of the notch. A midrib is formed behind the notch and the prothallus grows to become asymmetrically cordate. The mature prothallus is naked and with ruffled wings. Juvenile leaves possess entire, naked lamina.