On Antheridial Metabolism in the Fern Species Onoclea sensibilis L.

Dopp (1) demonstrated that the extract from mature prothalli of the fern species Ptcridiwtn1 aquiilinunil (L.) Kuhln hastened the onset of antheridium formation in young prothalli of this species by several days and in the prothalli of Dryopteris filixwwlas (L). Schott by several weeks. Dopp's conclusion that the prothalli of P. aquilinit elaborate a specific antheridium-inducing factor was confirmed. Conditions were defined under which the prothallial extract and the mediunm of 4 to 6-week-old cultures of P. aquilinion were mlostly active to a dilution of 1: 30,000 if assayed against the prothalli of the fern sp)ecies Onoclea sensibilis L. (4, 8, 10). The prothalli of this species proved ideal for assaying antheridiuminducing activity for various reasons (3, 4, 8, 10). Using this assay, the active substance was isolated and partially characterized (11, 12). The prothalli of 0. scuisibilis (5) and of P. aqutilin1um (3, 5) lose their competence to form antheridia in the presence of the antheridial factor soon after they attain heart-shape. In 0. sensibilis the loss of sensitivity to the antheridial factor is completed within a period of less than 2 days (5). ('nce the prothalli are insensitive they fail to form antheridia even if the antheridial factor is supplied at a concentration 15,000 times higher than that sufficient to induce antheridia in younger prothalli. Surgical experiments led D6pp (2) to concludle that this loss of sensitivity must be ascribed to a substance, termed by him the H-Substanz, which is elaborated by the meristem of the maturing prothallus. The present report is concerned with the question why Onoclea prothalli fail to form antheridia spontaneously under the prevailing conditions of culture. Earlier studies indicated that the maturing Onoclea prothalli did elaborate somle antheridial factor, even though they failed to form antheridia at all stages of development. It mutst be pointed otut that tlh C last individuials of the gametophyte population became inseinsitive to the antheridial factor 2 to 3 days before the first trace of antheridium-iniducing activity could be detected in the medium (7). The results thuts inidicated that the failure of Olioclea lprothalli