2 2 Ward . — Recent Researches on the Parasitism of Fungi. 
grow out of the cell into a mycelial form, which in due time extended 
and developed uredo-patches on the leaf. 
The first assertion of this extraordinary hypothesis by Eriksson 
appears to have been made (63 and 64 ) in 1897, and the principal grounds 
on which he based it were, so far as I can discover, the following : — 
(1) Certain forms — i. e. cultivated varieties — of Wheat always show 
rust in a short interval after sowing, e. g. 4-5 weeks, no matter what time 
of year the seed is put into the ground. But it should be noted that, 
in Sweden, the rust appears in summer earlier on winter-sown than on 
spring-sown crops. 
(2) The Barberry, which carries the aecidial form of P. graminis ; the 
two species of Rhamnus which carry the aecidia of P. coronata and P. coroni- 
fera respectively ; and the Boragineae which bear the aecidia of P. dispersa , 
are by no means always present in the neighbourhood of these sudden out- 
breaks of rust, and cannot possibly be credited with the infection. Similar 
statements have been made by others — e.g. Barclay ( 3 ) in 1892 pointed 
out that P. graminis appeared in India at a distance of 300 miles from any 
Barberry; Cobb ( 40 ) in 1891 had assumed that the uredo-form must be 
perennial in Australia, and so on. 
We may safely accept the fact that outbreaks of rust frequently occur 
at distances so remote from any plant known to carry the aecidial form, 
that it is almost impossible to believe that spores blown from such plants 
are responsible. 
(3) Dismissing the probability of wind-blown aecidiospores as explain- 
ing the outbreaks, Eriksson proceeds to demolish the idea that lurking 
uredospores, which have passed the winter in the died-down stocks of 
grasses, may be responsible for the outbreaks. 
Here we may note that De Bary in 1865 ( 20 , p. 23) had sought in 
vain for a perennial mycelium of P. graminis , persisting through the winter, 
in Agropyrum repens and Poa pratensis ; and Eriksson confirmed this in 
1896 ( 62 , p. 40), and also failed to find any such wintering uredo on 
Dactylis glomerata or Agrostis vulgaris. 
On the other hand, Blomeyer in 1876 ( 34 , p. 405); Rostrup in 1884 
( 147 ); Plowright in 1882 ( 132 , p. 234); Kuhn in 1875 ( 101 , p. 401); 
Hitchcock and Carleton in 1893 ( 85 , p. 11); and Bolley in 1898 ( 30 , 
p. 894), specifically demonstrated that the uredospores can live through the 
winter on Wheat. 
(4) But the principal evidence on which Eriksson relies is, perhaps, 
that obtained by growing Wheat, &c., in glass cases in his experimental 
fields. 
Herewith I append a summary and analysis of these experiments, 
compiled from Eriksson’s account: — 
