SOME OBSERVATIONS ON THE EGGS OF FUCUS AND UPON THEIR MUTUAL INFLUENCE IN THE DETERMINATION OF THE DEVELOPMENTAL AXIS

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Abstract
Results of observations and experiments are presented which relate to the nature of the Fucus egg and to some of the changes which take place in it at fertilization. Giant eggs, which in some cases develop supernumerary rhizoids, originate in the fusion of single eggs within the capsule, especially at the time of emerging from it. The extent to which eggs fuse is greatly increased at higher temperature. Cross fertilization does not take place between F. vesiculosus and Ascopkyllum nodoswm, and the antherozoids of F. evanescens do not fertilize the eggs of F. vesiculosus to any appreciable extent. Individual receptacles of the monoecious F. evanescens are entirely self fertile. The developmental axis of the spores is directed by the presence of nearby neighbors in F. vesiculosus, F. evanescens, and in Ascophyllum. The rhizoid protrudes in the resultant direction of neighbors. No solid egg substance traverses the space between affected eggs. Unfertilized resting eggs of another species direct the division planes of the eggs of F. evanescens equally as well as dividing eggs of the same species. The directive effect cannot be ascribed to any agency dependent on nuclear or cell division in the directing cells.

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