THE PROTHALLUS OF TMESIPTERIS TANNENSIS. 789 



Tmesipteris. When such structures become strictly saprophytic they not only lose 

 all trace of chlorophyll in their cells, but they nearly always become symbiotically 

 associated with a mycorrhizal fungus. To this rule Tmesipteris is no exception. It 

 is strictly saprophytic. It bears no chlorophyll in its tissues, but becomes infected 

 with an endophytic fungus. In many saprophytic Pteridophyte prothalli the endo- 

 phytic fungus becomes localised in certain definite regions of the prothallus. This 

 seems not to be the case in Tmesipteris. The fungus here seems to infect any of the 

 cells in the vegetative tissue of the prothallus. This is shown in figs. 4, 5, and 6. 

 It is a very definite and conspicuous thread-like mycelium which enters into the 

 interior of the cells, forming long coil-like structures in the protoplasm of the host 

 cells. The endophytic fungus is certainly more conspicuous in the surface cells and 

 those near the surface, but, as shown in sections and as illustrated in fig. 6, the 

 infection may extend into the very interior of the prothallus. I cannot say whether 

 the fungus ever infects the archegonial cells, because none of my specimens showed 

 the early unfertilised stages of the archegonium. Although many older archegonia 

 were found, none of their cells showed the endophytic fungus. This was also 

 observed to be the case in regard to the antheridia. Here both young and old stages 

 were found, but in none of the antheridial cells was the fungus observed. In this 

 connection it should also be noted that in the case where the young stages of 

 the embryo were observed, as shown in figs. 6 and 16, none of the embryo cells 

 appeared to be infected. This absence of the fungus from the embryo cells — -which 

 of course may not prove to be general — made it possible for a. sharp contrast to be 

 drawn between the cells of the young sporophyte and the cells of the surrounding 

 gametophyte which contain the fungus (fig. 6). The young sporophyte, however, 

 does later become infected by what certainly appears to be the same fungus that 

 infects the gametophyte. 



In the gametophyte tissue the endophytic fungus evidently provides all the 

 necessary food for its host. And if one may judge from the appearance of sections, 

 it would seem that the fungus may remain within the protoplasm of the host cells 

 without causing immediate destruction. But the appearance of older infected cells 

 makes it quite clear that the fungus eventually causes the death and disintegration 

 of the cell contents it infects. As indicated in figs. 4 and 5, the nucleus seems to be 

 quite normal, but as the fungus increases within the cell the nucleus appears to 

 undergo a gradual change, and finally disintegrates along with the other protoplasmic 

 structures of the host cells. As far as I have been able to judge, it would seem that 

 the prothallus becomes infected at a very early period, and I am inclined to believe 

 that the endophytic fungus is necessary for the germination of the spore. I shall, 

 however, go into this matter more in detail in a future paper. 



There is evidently no differentiation of the prothallus into reproductive and 

 vegetative regions. As we would expect to find in prothalli of subterranean habitat, 

 the antheridia and archegonia are produced on the same individual. These reproduc- 



