Laminaria digitata, L. saccharina, L. hyperborea, brown algae. Release of zoospores in a cross-section of the thallus, movement and settlement of zoospores on substrate, vegetative growth phase of gametophyte, development of oogonium, emergence of egg, formation of antheridia, spermatozooids swarming to egg cell, differentiation of the zygote, early development of the sporophytes.