12 HUMPHREY 



color. Upon careful examination it was found that they were 

 in a dying condition owing to the presence of a fungus. A 

 large quantity of material consisting of plants in a normal con- 

 dition as well as those visibly affected by the fungus were 

 brought into the laboratory in September, 1906, where the rela- 

 tion of fungus to host could be more carefully studied. This 

 species of Aneura is found growing on moist surfaces of rocks 

 along streams, on decaying logs and moist banks of soil in 

 which there is considerable clay. Material collected from all 

 three of these sources contained a large number of infected 

 plants so it is hardly probable that the fungus is one confined 

 to plants growing on decaying wood. 



Aneura multijida major ^ as well as other species of this genus, 

 under certain conditions produce two-celled gemmse in great 

 numbers. It was found that many of these after a short time 

 had germinated and some were infected. Figure 15 shows a 

 young plant resulting from the germination of a gemma, into the 

 older cells of which a fungus had penetrated by well-marked 

 haustoria. The diseased cells contained less chlorophyll and 

 showed unmistakable evidences of the harmful effect of the 

 fungus. Young plants of varying age and size were found to 

 be infected. It was first thought likely that infection took place 

 directly while the gemma was still within its mother cell, but a 

 very careful examination of gemmae failed to support any such 

 view. It seems that young plants of less than four cells are 

 rarely infected. The fungus develops conidia freely and it is 

 probable that infection is brought about by their germination. 

 A small number of young plants developing from germinating 

 spores were observed, but as yet none of these has shown the 

 presence of a fungus. 



In the older plants, hyphse from within the cells of the thallus 

 grow downward extending into the rhizoids, though this is by 

 no means so common as in the case of Fossombronia or Fim- 

 brlaria. Many rhizoids whether infected or not present a 

 strong tendency to branch as shown in Fig. 16, a and h. This 

 is undoubtedly due to the influence of contact stimulus ; in fact, 

 rhizoids not in contact with the substratum are all quite simple 

 and more delicate. 



