in the Bromes and their Brown Rust . 265 
ascertaining the conditions of germination of the Uredospores. 
De Bary, Plowright, Eriksson, Duggar and a few other ob- 
servers have given some facts of a general nature, but it 
seems probable that the subject would repay much closer 
investigation. 
I have, during the course of the experiments, tested various 
factors which seemed to be influencing the germination of 
the spores, but it should be borne in mind that the investiga- 
tion of the temperature effects was not part of the original 
plan, and it was not until my attention was directed to them 
by the failure of infection under circumstances (see p. 291) 
which left little room for doubt that high ^temperatures were 
interfering with the process, that I went further into these 
points. 
From the ease with which infection occurs at all ordinary 
temperatures, it seems to have been generally taken for 
granted that Uredospores will germinate at almost any 
ordinary temperature in Summer. As matter of fact this 
is not the case, and new light is thrown, I think, on some of 
Eriksson’s results by the recognition of the cardinal points 
here brought forward. 
I found that the spores germinate readily in ordinary light 
or in darkness, in red but not so readily in blue light, in 
ordinary water or in decoction of the leaves of Bromus , in 
water containing green Algae, fibres of paper-pulp, or even 
germinating spores of other fungi, provided the temperature 
did not rise beyond 25 0 C or thereabouts, and that the spores 
themselves were properly ripened and fresh. 
The best results were obtained with spores gathered early 
in the morning, before the dew is off, from leaves still green 
and fairly young. This is undoubtedly because later in the 
day the ripest spores have been shed, and because exhaustion 
has set in on older leaves. 
The following Table (VII) seems to bring out these con- 
clusions very clearly, though the temperature of germination 
is somewhat high for the species. 
In reply to the criticism that the non-germination of Uredo- 
T 
