Development of adventive embryos in cauline leaves of Sargassum macrocarpum (Fucales, Phaeophyta)

SUMMARY Spontaneous formation and development of adventive embryos were observed in cauline leaves of Sargassum macrocarpum in laboratory culture. Semi-spherical swellings, which were 200–250 μm in diameter, arose from the surface of cauline leaves of thalli cultured for 4 months from zygotic embryos. Swellings became cylindrical protuberances and grew into ‘daughter’ thalli with one or two small cauline leaves. These thalli detached from ‘mother’ thalli and attached to the surface of culture vessels by rhizoids produced within 1 week after detachment. Each daughter thallus developed into an individual thallus exhibiting the same morphological processes as zygotic embryos.