The Formation of Zoospores in Undaria undarioides (Yendo) Okamura

Abstract

1. At the first nuclear division in the zoosporangium of Undaria undariaides (Yendo) Okamura, synapsis stage and diakinesis are observed. Therefore, the first and second nuclear divisions in the zoosporangium are meiosis.
2. After meiosis, three successive mitoses take place to form 32 free nuclei. Consequently 32 haploid zoospores are contained in a zoosporangium.
3. The haploid chromosome number in the present species is about 30.
4. Both the centrosome and the aster are not observed. The spindle is delicate.
5. The nucleolus disappears at late diakinesis.