PROTONEMA WITH GIANT NUCLEUS IN SIPHONACEOUS GREEN ALGA BRYOPSIS HYPNOIDES AND ADDITIONAL CYTOLOGICAL RESULTS

Zygotes of Bryopsis hypnoides, maintained in modified Schreiber-solution, germinate into a rhizoidal protonema with a single nucleus; the nucleus diameter increases up to eight times that of vegetative nuclei in the multinucleate thallus. The giant nucleus contains a long sinuous nucleolus similar to that of Acetabularia. The protonema becomes multinucleate prior to the formation of the plumose thalli. The division of the giant nucleus has been observed: Chromosomes in mitotic configuration, apparently diploid, become visible at the periphery of a large dumbbell-shaped spindle formed by the dividing nucleolus. Subsequently, the giant nucleus dissolves and dismisses two small nuclei, which propagate mitotically. Further observations deal with the persistence of the nucleolus during mitosis, chromosome number, gamete formation, and gamete copulation. © 1969 Biologischen Anstalt Helgoland.