Rhizoid Differentiation in <i>Fucus</i> Eggs Labeled with Calcofluor White and Birefringence of Cell Wall

Abstract

The cell wall of Fucus evanescens eggs, at about 2 hours after liberation from receptacles, was labeled with the fluorescent dye, calcofluor white M2R, and the eggs were cultured in normal sea water. Later, at various times, the fluorescence was inspected. The results were as follows. (1) The cell wall was uniformly labeled in the beginning. (2) The peculiar region exhibiting a specially high fluorescence appeared before actual formation of the rhizoid protuberance. (3) The distal region of the protuberance was almost defective of the fluorescence, while the basal region exhibited a specially strong fluorescence. Observation with a polarizing microscope revealed that birefringence of the cell wall is uniformly characterized in early stages, but a region of a strong birefringence appears just before the actual formation of the rhizoid protuberance. The distal cell wall of the protuberance exhibits very faint, while the basal cell wall displays very strong birefringence. From these observations, it seems that the rhizoid protuberance is not a mere transformation by protrusion of the corresponding region of the former cell, but it is accompanied by a de novo formation of the cell wall and cytoplasm.