Differential recognition of the outer and inner walls of epidermal cells by a rust fungus

is the pheromone factor mediating chemotactic approach to the female cell in Syringoderma. Multifidene was found to be less active by a factor of 100. This result conforms well with the present state of knowledge on brown-algal pheromones outlined above. Ectocarpen, the male-attractant of Ectocarpus is found as an apparently nonfunctional by-product in Cutleria, Laminaria, and Desmarestia. A new similar case is now apparent, where the attractant of Syringoderma is also found as a by-product in the egg secretion of Desmarestia. Due to the lack of data on sexual reproduction of Syringoderma and Desmarestia in the natural habitat it is not possible at present to evaluate a possible interference of both species on the level of sexual pheromones.