786 PROFESSOR A. ANSTRUTHER LAWSON ON 



a quarter of an inch in length, and about three-sixteenths of an inch at its broader 

 end. It tapered off to a point at the opposite end, and had the general appearance 

 and symmetry of a prothallus of a certain species of Lycopodium. Lang identified 

 two regions in the prothallus, as in Lycopodium — a lower vegetative region and a 

 wider upper region to which the reproductive organs were confined. The lower 

 vegetative region was of a brown colour and bore numerous rhizoids. The structure 

 is subterranean in habitat, wholly saprophytic, and seems to correspond to the type 

 of prothallus of Lycopodium clavatum or complanatum. It bore several antheridia, 

 but no evidence of archegonia or embryo was revealed. Since only one specimen 

 was found, the knowledge derived from its study is very fragmentary, and there was 

 no real evidence to prove that the prothallus described is really that of Psilotum. 

 Doubt certainly exists, and the uncertainty is freely acknowledged by the discoverer. 

 In regard to the other genus of the Psilotacese, nothing whatever concerning 

 the prothallus has so far been recorded. We have no knowledge of the gametophyte 

 generation or embryo of Tmesipteris. With the exception of the doubtful and very 

 uncertain prothallus described by Lang, our knowledge of the gametophytes and 

 embryo of the Psilotacese may be regarded as a complete blank. 



It seemed therefore to me, upon my arrival in Australia in February 1913 to 

 occupy the Chair of Botany in the University of Sydney, that an opportunity had 

 at last offered itself for filling in this interesting gap in our knowledge of the 

 Pteridophytes. A day or two after my arrival I learned that both Tmesipteris and 

 Psilotum were to be found growing in great abundance in the immediate vicinity of 

 Sydney. It was hoped that a careful search would confirm Lang's account of 

 Psilotum and reveal the gametophyte of Tmesipteris. After close attention to this 

 matter,- I am now happy to be able to report that my efforts have been .partly 

 successful. I have discovered several specimens of a structure which I believe un- 

 doubtedly to be the prothallus of Tmesipteris, and a single specimen of a structure 

 that I believe to be the prothallus of Psilotum. The latter structure, however, bears 

 no resemblance to the supposed prothallus described by Lang. 



In the search for the prothalli of these plants two methods were followed. Search 

 was made in the field for the prothalli as they occur in nature ; and spores were sown 

 in various media with the hope of their germinating and developing prothalli. In 

 the latter method many attempts were made to cause the germination of the spores 

 in the soil in which Tmesipteris and Psilotum sporophytes were growing. A soil 

 was made by taking the surface from the trunks of Dicksonia, Alsophila and Todea, 

 on which Tmesipteris grows very freely. It is also a fact to note that Tmesipteris 

 grows quite freely in soil in nature, as well as on tree trunks ; and such soil was also 

 taken as a medium in which to germinate the spores. Cuts were made in the tree 

 trunks with a sharp axe, and in the cleft thus made spores were abundantly sown. 

 Similar experiments were made with Psilotum. It sometimes happens that Psilotum 

 and Tmesipteris grow together under very similar conditions, but this is rather the 



