Ward . — Recent Researches on the Parasitism of Fungi . 2 1 
My researches, published in 1902 ( 190 , p. 302), for which I claim 
greater exactness in measurement, counting, &c., than had hitherto been 
attempted, showed that the curves of infectibility and of numbers, sizes, &c., 
of stomata, hairs, and so forth, not only do not correspond, but they show 
no relations whatever ; and clearly led to the conclusion that the matter has 
nothing to do with anatomy, but depends entirely on physiological reactions 
of the protoplasm of the Fungus and of the cells of the host. 
In other words, infection, and resistance to infection, depend on the 
power of the Fungus-protoplasm to overcome the resistance of the cells 
of the host by means of enzymes or toxins ; and, reciprocally, on that of 
the protoplasm of the cells of the host to form anti-bodies which destroy 
such enzymes or toxins, or to excrete chemotactic substances which repel 
or attract the Fungus-protoplasm. 
The histological examination of the host naturally led to the investiga- 
tion of the microscopic characters and behaviour of the Fungus in the 
tissues of the host. 
This was done, and the results published in a paper on the Histology 
of P. dispersa ( 195 ) in 1903, in which I demonstrated the whole course 
of normal infection, the development of the haustoria, the behaviour of the 
nuclei, and the growth of the Fungus in the leaf of the Brome. 
Eriksson’s Hypothesis. 
The necessity for this thorough examination of the host and parasite, 
and their mutual behaviour one towards the other, had become the more 
imperative in view of the extraordinary position which had been taken 
up by Eriksson, than whom no man had earned a better right to speculate, 
be it said, with regard to epidemics of rust. 
Eriksson, it will be remembered, had been driven by the results 
of experience in the field to conclude that the enormous epidemics of 
rust which break out so suddenly, at certain seasons, cannot be explained 
by the incidence of normal infection by wind-blown uredospores. 
He therefore framed the hypothesis that the Fungus is able to so com- 
bine some of its living protoplasm with the living protoplasm of the host, 
that a condition of symbiosis is established, both remaining alive and 
capable of passing from cell to cell of the host-plant. 
This symbiotic union Eriksson termed Mycoplasma — a word we trans- 
late Mycoplasm. This mycoplasm was assumed to be capable of remaining 
dormant in the leaf, or even in the seed into which it had passed, for many 
weeks or months ; and then, under favourable circumstances of the environ- 
ment, the fungal element — hitherto unrecognizable by any method known 
to us — would suddenly sort itself out, assume morphological autonomy, and 
