Ultrastructure and Differentiation In Chara Sp. III. Formation of the Antheridium

Abstract

The formation of the antheridium from an enlarged nodal cell is described. After a basal cell has been cut off, precisely oriented mitoses divide the antheridial cell initially into octants; then follow two periclinal divisions in each octant. The outer layer of cells become the shield cells, the middle form the manubria, and the inner capitula cells divide further to produce secondary capitula and ultimately the spermatogenous threads. The shield cells become compartmentalized during enlargement by ingrowths in the wall which finally form a very distinctive pattern. Microtubules are associated with the regions of wall deposition. Plastids in the shields accumulate large numbers of globuli, and this is probably associated with the orange pigmentation they acquire. Large amounts of material seem to be secreted into the antheridia by the manubria; this material is formed within large vesicles which are apparently discharged through the plasmalemma. In the young capitula, a characteristic, highly organized grouping of many cytoplasmic microtubules forms a band which appears to wind through the cytoplasm; its significance and functions are obscure. Presumptive "spherosomes" are present in large numbers in these and spermatogenous cells. The spherosomes and lipid-like inclusions are very frequently coated with membranes of the endoplasmic reticulum.