Changes in the Level of the Protein Nitrogen during Growth of the Gametophyte and the Initiation of the Sporophyte of Dryopteris borreri Newm.

Abstract

Estimations of the amounts of organic nitrogen in spores and developing gametophytes of Dryopteris borreri, a fern reproducing apogamously and lacking archegonia, have shown that the nitrogen in the gametophytes increases exponentially. The logarithmic rate of increase of the nitrogen remains unchanged during the initiation and emergence of the sporophyte. Gametophytes about to produce sporophytes yielded only filamentous growths when transferred to a medium containing 8-azaguanine, and the increase in their content of organic nitrogen was very small. The results are discussed in relation to similar estimations made by other workers upon the gametophytes of Dryopteris erythosora(Eat.) Schott, a fern reproducing sexually. The interpretation placed upon the results obtained for D. erytkrosora is questioned, and a new interpretation of these results, together with those for D. borreri, is related to the difference in morphology of the two generations in the life cycle of the Polypodiaceous ferns.