Puccinia malvacearum and the Mycoplasm Theory. 
BY 
M. A. BAILEY, B.A., Cantab. 
With two Figures in the Text. 
Introduction. 
HE sudden and widespread appearance, year after year, of certain 
J- parasitic fungi is a phenomenon which has been recognized for many 
years and has given rise to the keenest controversy and speculation. 
The mode of origin of these epidemics is very difficult to discover, 
and the question is rendered more complex owing to the fact that the fungi 
concerned are often extremely narrowly specialized and that their spores 
frequently show a very limited period of viability. 
After a lengthy series of experiments on the Rusts of various species 
of Gramineae, Eriksson brought forward the Mycoplasm Hypothesis in 
explanation of the observed facts. 
This hypothesis was first asserted by him in 1897, but has been 
developed and enlarged upon subsequently to include other fungi in addition 
to the Cereal Rusts. 
In 1911 Eriksson published a monograph on Puccinia malvacearum } 
in which he applied this theory to account for the yearly origin and 
dissemination of the Hollyhock Rust, and more recently a similar explana- 
tion has been put forward by him in the case of the Potato Disease Fungus, 
Phytophthora infestans , 2 Briefly stated, his suggestion is that the fungus, 
in certain cases, is able to spend part of its vegetative life in the form of 
naked protoplasm in the interior of the cells of the host, existing there in 
a symbiotic state. 
When in this condition the fungus is said to have assumed the myco- 
plasmic state, and this mycoplasm permeates the whole of the plant tissues, 
including the developing embryo. 
1 Eriksson : Der Malvenrost ; seine Verbreitung, Natur und Entwickelungsgeschichte. Kungl. 
Svenska Vetenskapsakademiens Handlingar, Band xlvii, No. 2. 
2 Eriksson : Developpement primaire du mildiou ( Phytophthora infestans ) de la pom me de 
erre. Rev. Gen. de Botanique, tomes xxix and xxx. 
[Annals of Botany, Vol. XXXIV. No. CXXXIV. April, rgao.] 
