IV.—The Gametophyte Generation of the Psilotaceæ

Abstract

Since the preliminary announcement of the discovery of the prothalli of Tmesipteris and Psilotum communicated to the Royal Society of Edinburgh in June 1916, a considerable amount of additional material has been found, and it seems therefore desirable to place on record a more detailed account of these interesting structures. The preliminary description, as published, was based upon but a few specimens, and these were not sufficient to reveal all of the vegetative and reproductive features, nor enough to justify any broad general conclusions as to the phylogenetic position of the Psilotaceæ. The discoyery, however, has filled in an important and interesting gap in our knowledge; for the Psilotaceæ are the very last of the known Pteridophytes to surrender their gametophytes to the light of science.