Ward. — Recent Researches on the Parasitism of Fungi. 13 
is probably right in saying that germination and infection occur better 
in dew and mist, alternating with sunshine, than in rain — apart from the 
fact that spores may be washed off during showers. 
But I have evidence to support the generally accepted view that 
external conditions of other kinds affect the germination of uredospores, 
as they are known to do that of other spores. 
That the temperature is an important factor must be conceded ; but 
it is surprising how little has been done in this connexion as regards 
Uredineae. I found ( 190 , p. 269) the optimum for Puccinia dispersa to 
be near 2o°C. ; the minimum being below io°-i2° C. ; and the maximum 
about 2 7 0 C. These uredospores failed to germinate at 3 o°C and were 
killed at 65 0 - yo° C. ; though their age and ripeness affect the matter. 
As regards age, De Bary found that the uredospores of P. graminis 
lost their capacity for germination in from one to two months. 
Klebahn ( 98 , p. 26) was able to infect with spores of Peridermium 
Pini after keeping them five weeks ; and with spores of P. Strobi after 
keeping twenty days. 
I found the uredospores of P. dispersa germinated after being kept 
dry for sixty-one days, and the experiments were only closed then for lack 
of material ; while Miss Gibson, working in my laboratory, kept aecidio- 
spores of Phragmidium for fifty-four days, and the uredospores of the 
Chrysanthemum Rust for ninety-four days, when they still germinated. 
Again the work had to be stopped, and we do not know how much longer 
they would have continued to live. 
Jacky, also, found the uredospores of the Chrysanthemum Rust 
alive after keeping them from December 1 to February 5, in gauze bags in 
the open ( 87 ). 
I can also give you a few other data, bearing out the same point. 
Barclay ( 2 , p. 234) gives as the limits of germination-capacity for various 
species, from two to eight months ; and Bolley ( 30 ) says that P. ‘ Rubigo- 
vera ’ infected after thirty days’ exposure to air and sunshine. 
Even in cases where the teleutospores do not germinate until the 
following spring, it is clear that facts such as the above will have to be 
reckoned with before any one can deny the possibility of a uredo being 
carried safely through the winter period. 
Further research — and the subject is a good one — will have to decide 
how far the climate, shelter, lurking in crannies or concealed in dry tufts 
of herbage, and so forth affect the matter. It is true that perennial mycelia 
have been sought for in vain in many of the forms here concerned ; 
nevertheless Magnus states that P. Caricis passes the winter in the uredo- 
stage, and the same is affirmed of others — e. g. by Dietel and Schroter of 
Uromyces Junci and Puccinia Luzulae , and by Barclay of P. coronata , 
the uredo of which he found throughout the winter in sheltered places. 
