Abstract
Pteris vittata sporelings were centrifuged at 2- and 3-cell stages of the protonema at 500 to 50, 000 times gravity. When a centrifugal force was exerted towards the basal direction of the protonema tip cell, the chloroplasts and nucleus were stratified in its basal end. In further culture of these basally centrifuged materials, an outgrowth occurred at the basal portion of the tip cells almost at 100 per cent, when the centrifugal force was stronger than 5, 000 times gravity and the length of tip cells was more than 300μ.
Such an outgrown cell continued to develop as a branching, finally giving rise to a mature gametophyte. Thus the original developmental axis was altered, and the original tip was basalized, sometimes forming a rhizoid at its apical portion. A discussion was given of aspect that the developmental polarity of this fern protonema is controlled by the localization of endoplasmic components rather than by the cortical cytoplasm which is hardly movable by centrifugation.
