THE PROTHALLUS OF TMESIPTERIS TANNENSIS. 787 



exception than the rule. The general rule is that the two plants require very 

 different habitats. Psilotum flourishes abundantly in exposed rocky places — especially 

 in the crevices of sandstone cliffs ; while Tmesipteris, on the other hand, requires 

 shady, moist conditions, especially in gullies near waterfalls. Spores of both plants 

 were sown in definitely marked places in the field, and have been examined from 

 time to time. Many of these experiments are still under careful observation. When 

 the results of these germinations are more complete, I hope to describe a detailed series 

 of stages. But in the meantime I propose to give a preliminary account of the mature 

 prothallus of Tmesipteris, as I have found several specimens associated with young 

 sporophytes in nature. The first of these specimens was found in the substance of 

 the outer part of the trunk of Todea barbara in the month of April 1914, at Bulli 

 Pass, N.S.W. 



In May of the same year a second specimen was found. Of the first specimen 

 found I had some doubts, for it showed neither antheridia nor archegonia, but I now 

 believe it to be a portion of the prothallus which was broken off from the rhizome 

 of a young sporophyte. This was to some extent confirmed by the discovery of the 

 second specimen, which showed undoubted antheridia and archegonia. From these 

 two specimens I felt certain in my own mind that I had at last been successful in 

 finding the prothallus, but as only one of them showed the reproductive organs, 

 I thought it better to delay publication until I had confirmed these preliminary 

 observations by the finding of other specimens. It was not until March and April of 

 1915 that I was able to find additional prothalli, and these I found at Mount Wilson, 

 on the trunks of Dicksonia. In this locality, which is quite one hundred miles north 

 of Bulli Pass, where the first specimens were found, two additional prothalli were 

 found. These were both in close association with very young sporophytes, and 

 showed exactly the same sort of structure as those found at Bulli. In one case 

 the prothallus was in actual contact with the rhizome of a young Tmesipteris plant, 

 but it became detached while removing the particles of soil and sand with a camel's- 

 hair brush. Later on in the same year an additional specimen was found at Sommerby 

 Falls, near Gosford, New South Wales, and I have since found others at Mount 

 Wilson. I have therefore no hesitation in definitely describing these specimens as 

 the gametophyte generation of Tmesipteris Tannensis. 



General Features of the Prothallus. 



Compared with the Lycopodiales and other Pteridophytes the prothallus of 

 Tmesipteris is small. The largest specimen examined measured just about one-eighth 

 of an inch in length and varied in thickness, being three or four times longer than 

 broad. It is practically cylindrical in form, but slightly wider at one end than 

 at the other, as shown in figs. 1, 2, and 3. The form, although in the main 

 cylindrical, varies considerably ; no two specimens showed the same shape, some of 

 them even showed branching. The method of its branching does not seem at all 



