On the Control of Antheridium Formation in the Fern Species Lygodium japonicum. ∗

Abstract

Summary

It is demonstrated that prothalli of L. japonicum elaborate, and secrete into the medium, a substance which controls formation of antheridia in this fern species. The antheridium-inducing activity of the medium is stable to boiling for 10 min at both pH 2 and 12. It is adsorbed on charcoal and destroyed by ashing. The results are considered to show that this antheridium-inducing substance differs from the substance which controls the same developmental event in many species of the fern family Polypodiaceae. The results further indicate that the Lygodium factor is also chemically distinct from the substance that controls antheridium formation in A. phyll∗ ∗ ∗itidis which, like L. ∗ ∗ ∗japonicum, belongs to the fern family Schizaeacea∗ ∗ ∗. The individuals that first attain the reproductive phase in a gametophyte population of L. japonicum give rise to one or 2 archegonia before the first antheridium initial appears. This sequence of sex-organ formation is reversed in the prothalli which subsequently attain the reproductive phase. All prothalli attain the archegonial phase first if they are isolated, one per flask, at an early stage of development. In contrast, all prothalli attain the antheridial phase first if they are all provided with the antheridium-inducing substance at an early stage of development. It is concluded that the more slowly growing individuals in a gametophyte population of L. japonicum attain the antheridial phase first because they respond to the antheridium-inducing substance that is elaborated, and secreted into the medium, by the more rapidly growing gametophytes.

I am grateful to Dr. Armin C. Braun for the encouragement he has given this investigation.