That this symbiotic association may occur in still lower 

 organisms than the ferns is shown in the familiar case of 

 the lichens, which are most perfect examples of this. It 

 has been shown also that a similar association of fungus 

 and host occurs in a good many liverworts. Cavers 8 has 

 studied this association with some care in the common 

 liverwort Fegatella, as well as in other Ifepaticic. He 

 found in Fegatella that the endophyte is beneficial to the 

 growth of the host, the plant being more vigorous when 

 the fungus was present. He assumed that this was due 

 to the assistance given by the fungus in the assimilation 

 of organic matter from humus or from other organic 

 substrata. 



This frequent occurrence of an endophyte in Hepatiea* 

 makes the occurrence of this in the green prothallia of 

 ferns quite readily understood. Whether in the latter it 

 is an advantage to the host to have the endophyte present 

 remains to be seen, but it is highly probable that such is 

 the case. Once having acquired the habit of associating 

 itself with the fungus, the gradual development of the 

 purely saprophytic subterranean gametophytes of the 

 Ophioglossaceae from green forms similar to those of the 

 Marattiaceae, is readily conceivable. In the genus Ly co- 

 podium there is every degree from the strictly holophytic 

 green prothallium of L. salakense to the subterranean 

 chlorophylless gametophyte of L. clavatum or the still 

 more specialized gametophyte of L. phlegmasia. 



Presumably in the Ophioglossaceae the evolution of the 

 gametophyte has been very much the same as in Lyco- 

 podium. 



•On Saprophytic and Myoorhiza in Hepaticjr. % New Phytologist. II. 

 1903. 



