230 THE PRESIDENTIAL ADDRESS. (Sess. Lxx1. 
and germinate in the next season, and thus a satisfactory 
explanation would be forthcoming of the occurrence of the 
epidemic. Eriksson, however, will have none of this, but he 
introduces what he calls “ the intracellular mycoplasm life of 
the fungus,” what he calls for shortness his mycoplasm theory, 
according to which, by some mysterious method, the proto- 
plasm of the fungus becomes combined in a long latent 
symbiotic life with the protoplasm of the host, forming a 
mycoplasm, and only shortly before the eruption of the 
rust pustules does it enter into a visible state assuming the 
form of a mycelium. Of this hypothesis Marshall Ward, 
aiter the fullest examination and discussion, was merciless 
in his condemnation. Savouring as it did of the fanciful. 
not susceptible of any optical demonstration, he would have 
none of it, and his last appearance at a meeting of botanists 
was at the British Association at Cambridge last year, when 
the question was fully discussed, and not to the advantage 
of Eriksson. 
On the recrudescence of the question of the nitrogen 
supply of green plants in 1886, brought about by the work of 
Frank on the mycodomatia of Leguminose and the mycorrhiza 
of forest trees, Ward entered the field, and by his discovery 
of the method of infection of the root hair and the subsequent 
stimulus of the root to the development of the mycodomatia, 
practically settled the question. Ward thought that the 
organism entering the root hair was a mycelial fungus. At 
that time the curious coenobial forms of bacteria had not been 
investigated. Now we know that Ward’s infection thread is 
really a bacterial colony. This does not detract from the 
merit of Ward’s discovery, which, as I have said, was crucial. 
Another critical piece of work was that in 1888 upon a 
disease of the lily, for in course of this he was able to show 
the exact method by which a fungus mycelium pierces the 
cell wall of its host, and to isolate the ferment by which the 
penetration is effected. 
In the middle eighties the organism known as the ginger 
beer plant came into special notice. Many botanists 
received specimens with requests for information regarding 
it. As you know, the plant consists of lumps of gelatinous 
substance which has been long in use in country districts 
for the manufacture of home-made ginger beer. When 
