174 Bailey. — Puccinia malvacearum and the My coplasm Theory . 
When the seed germinates in the following season, the fungus proto- 
plasm divides with the cytoplasm of the host cells and is in this way 
distributed throughout the tissues of the seedling plant. 
Later on, when the growing plant reaches a certain stage of maturity, the 
fungus reverts to the mycelial condition preparatory to the production of 
spores. 
The theory is exceedingly attractive and is backed by a mass of data 
derived from experimental inoculation and histology. If proved correct, it 
would have most far-reaching effects in modifying the theory and practice of 
the control of plant disease. 
Eriksson’s hypothesis has, however, many opponents, and certain 
isolated experimental results, recorded by other investigators, suggest that ! 
the facts can be explained by other and simpler means. 
It was with the idea of throwing further light on this subject that the 
experiments described in the present paper were started. 
The experiments were interrupted by the war, and there seems, { 
unfortunately, to be little chance of repeating them in the near future, but 
the evidence obtained is, in many cases, in such marked opposition to the 
observations and deductions made by Eriksson as to seem to warrant 
publication in some detail. 
The work was carried out at the John Innes Horticultural Institution, 
where I was given every facility through the kindness of Mr. Bateson. 
I should like to take this opportunity of thanking Mrs. Scott Tucker 
and Miss D. M. Cayley for great assistance rendered in the recording of 
results during the later stages of the experiments. 
An extensive bibliography is considered to be unnecessary in this 
paper, as a list of the more important literature will be found at the end of 
Eriksson’s paper on ‘ Der Malvenrost ^ already referred to. 
Discussion of Eriksson’s Work on the Hollyhock Rust. 
In his paper on the Hollyhock Rust, Eriksson emphasizes a number of 
points which he considers as affording strong evidence of the existence of 
a mycoplasmic stage in the life-history of the fungus. These points are 
enumerated below, where they are considered in the light of further evidence. 
i. Sudden appearance of the disease in epidemic form. This has long 
been recognized by many observers. Eriksson states that the interval 
between the sowing of the seed and the appearance of the disease in quantity 
is extremely regular and varies only with the time of year. Seed sown in 
Sweden at the end of June produced plants on which the rust appeared 
regularly about three months later. On no occasion did the plants show 
rust earlier than three months after germination, except in those cases 
where they were grown close to other plants which were already suffering 
from the disease. 
